Supermagzzz's blog

Codeforces Round #697 (Div. 3)
By Supermagzzz, 4 years ago, translation, In English

Hello, Codeforces! Were you afraid of the lack of contests? We also!

Unfortunately, due to technical problems, the round is declared unrated. You can continue to solve problems, but the results of the current round will not affect your rating. We are sorry for this situation.

<almost-copy-pasted-part>

Hello! Codeforces Round #697 (Div. 3) will start at Jan/25/2021 18:00 (Moscow time). You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 7 problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as trusted participants of the third division, you must:

  • take part in at least two rated rounds (and solve at least one problem in each of them),
  • do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

The problems for this round were invented by MikeMirzayanov and prepared by me Supermagzzz and Stepavly

Thanks to MikeMirzayanov for platforms and coordination of our work. Thanks to darkkcyan, Tzak, bfs.07, songsinger, iankury, spookywooky, Programmer, sodafago, infinitepro for help in round preparation and testing the round.

Good luck!

</almost-copy-pasted-part>

UPD: Editorial is ready!

  • Vote: I like it
  • +244
  • Vote: I do not like it

Comments Comments (369)
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4 years ago, # |
  Vote: I like it +36 Vote: I do not like it

7 Problems!!! Great.

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4 years ago, # |
  Vote: I like it +60 Vote: I do not like it

As a tester I would like to thank iankury for providing clear explanation.

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4 years ago, # |
  Vote: I like it +191 Vote: I do not like it

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4 years ago, # |
  Vote: I like it +12 Vote: I do not like it

Some brazilian testers, this is great!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Hope this contest will increase our rating!! Finger crossed.

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    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    I will try my best to reach pupil today. All the best to all participants.

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4 years ago, # |
  Vote: I like it +6 Vote: I do not like it

I was afraid, but why that happened? contest frequency is decreased this month than other months.

Thanks for the contest.

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4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

My chance for pupil!

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4 years ago, # |
  Vote: I like it +16 Vote: I do not like it

How can I become a tester for Div. 3 contests if I am not a friend of the testers/setters?

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    4 years ago, # ^ |
      Vote: I like it +37 Vote: I do not like it

    I am not a friend of either of them. I think it's pure random ;)

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      4 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      Thanks for your reply!

      Since I am less likely to give CP contests in the following few months, it would be nice for me to contribute to the CP community by becoming a tester for Div. 3 contests.

      I would want to become a Div. 3 contest tester in the future — if Stepavly and Supermagzzz would want me to provide feedback for your contests, please give me a call!

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        4 years ago, # ^ |
          Vote: I like it +14 Vote: I do not like it

        Well, this time each tester has a ten years badge.

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4 years ago, # |
← Rev. 2   Vote: I like it -17 Vote: I do not like it

.

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4 years ago, # |
  Vote: I like it +117 Vote: I do not like it

IMG-20210124-230053.

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

7 problems! Wonderful start after an eternal gap.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Are the registrations closed??

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

if i don't get 150+ rating i will do whatever the highest rated reply asks.

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4 years ago, # |
  Vote: I like it -104 Vote: I do not like it

I am sure nobody likes to see this. 20210125-004915

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I don't like seeing <"almost-copy-pasted-part>"

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4 years ago, # |
  Vote: I like it +45 Vote: I do not like it

As a tester, I recommend participants to open https://mirror.codeforces.com/contest/<contest-id>/problems rather than opening each problem page, during the contest.

Reduces clutter and server load (ig).

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4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

Thanks to Supermagzzz and Stepavly for preparing the div.3 contest.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

After the last contest when it was showing no contest for near future, it was a little bad feeling but now this contest has filled us with new enthusiasm(mind the spellings).

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Hoping for less plagiarism in the contest!

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4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Hello everyone its the first div3 of this year and i am here to wish you all good luck for today. Have fun guys.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Hoping for a great contest.

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

anyone having difficulties reaching codeforces ?

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

This round has got a crazy number of registrants ~26000, let's hope the round goes smoothly

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    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    I already can't visit codeforces.com but I can visit this blog for some reason

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Wish the pretest becomes strong.

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4 years ago, # |
← Rev. 2   Vote: I like it +36 Vote: I do not like it

To all my Indian brothers and sisters Happy Republic Day in Advance. 26th of January is celebrated as Republic Day in India to mark the day when the Constitution of India came into effect. JAI HIND

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4 years ago, # |
  Vote: I like it +30 Vote: I do not like it

Delayed. :(

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

28k people o_o

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    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    I don't even know if that's good or bad lol

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4 years ago, # |
  Vote: I like it -9 Vote: I do not like it

3 2 1 .....burrrr!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

oh no contest was delayed for 15 mins :(

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Dude, 28000+ registrations already, is this the highest up until now ?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Best of Luck Everyone. I wish you all get green in first try:)

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

15 minutes delayed. Drink some water to keep yourself hydrated.

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4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

delay is better than unrated.

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4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Hope the delay is for good cause. Submissions to be judged fast

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4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

garam kar k thanda hi chor diya

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

waiting for 30k?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

For a few seconds, I thought that problems are repeated:)

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4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

To All the Indians Happy Republic Day in Advance.

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4 years ago, # |
  Vote: I like it +7 Vote: I do not like it

This round is approaching 30,000 participants. This is year's first div 3, right ? Looks like some people are taking their new year's resolution seriously :P

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

My goodness. See the crowd!! It's highest among all contests that held in cf. Congo cf!

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Delayed by 15 minutes. And now I am spending time in the comments section.

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4 years ago, # |
← Rev. 2   Vote: I like it -33 Vote: I do not like it

deleted

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Is it the most popular round?

Have Fun & Good Luck!

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4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

with that many registrants if i get 3000th position I should be proud

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4 years ago, # |
  Vote: I like it +179 Vote: I do not like it

Sorry for the delay.

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4 years ago, # |
  Vote: I like it -51 Vote: I do not like it

HAPPY REPUBLIC DAY TO ALL MY INDIAN BROTHERS AND SISTERS IN ADVANCE

**** **** JAI HIND

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I was waiting this contest. Good luck geeks!

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4 years ago, # |
← Rev. 2   Vote: I like it +69 Vote: I do not like it

I am excited to see what SecondThread will be doing in these 15+10 minutes in his stream.

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

The servers seem to be struggling...

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4 years ago, # |
  Vote: I like it +34 Vote: I do not like it

Me After Seeing The Delay:-

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4 years ago, # |
  Vote: I like it +14 Vote: I do not like it

All the best MikeMirzayanov. 30k incoming!!!!

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4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Highest registered participants.

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4 years ago, # |
← Rev. 3   Vote: I like it +11 Vote: I do not like it

Congratulations CF on achieving a milestone of 29k participants.

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4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

another delay?

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4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Delayed 10 more minutes ?

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4 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Instead of delaying they should close the registration lol.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

How come again a delay?

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Again it's delayed by 10 mins!!!!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I think that reason of this delay is good skill for getting more and more participants

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4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Again delayed :(

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4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

What is going on??

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why delayed again?

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Waiting for 30k ?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

8:30 ??

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4 years ago, # |
  Vote: I like it +17 Vote: I do not like it

It seems it will be delayed until half of the participants go to sleep and we will deal with a normal number of participants.

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    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    nice joke, but staff of codeforces is not laughing now

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I think they will delay it until 30k people register:)

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4 years ago, # |
  Vote: I like it +19 Vote: I do not like it

I think they are waiting for 30k

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

contest is too much delayed :(

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

reschedule this contest.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

common I am not having dinner just because of the contest and it's getting delayed....

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

More delay but hopefully rated

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

it's Monday morning I was just trying to get a quick competition in.. now two delays?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Contest registrations are increasing by O(1) complexity xD

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

almost 30 thousand registrants ... that's huge!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

30K lmao....hope to become Expert Today

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

DelayForces !

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Close to 30k..!! May all registered participants give the contest.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

More 10 Minutes to wait :(

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

GOT DELAYED AGAIN 10 MIN 300 ppl left to the 30k

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4 years ago, # |
← Rev. 3   Vote: I like it +1 Vote: I do not like it

did it just got delayed again? just hope there will be a long queue in the contest. they might be updating pre-test cases due to 29k participants. in order to prevent long queue. (just my guess). good luck to all including (people who made this round.)

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

What is wrong? Contest has been reschedule twice already :|

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Can you reschedule the round again?

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Don't extend it again

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4 years ago, # |
  Vote: I like it +6 Vote: I do not like it

Are you kidding me?

That contest is put off 10min again means I couldn't get at least 4h to sleep in CHN.

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Div-3 be like.. wait 10min more..;)

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4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

CODEFORCES

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why the contest is delayed?

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4 years ago, # |
  Vote: I like it +17 Vote: I do not like it

→ Reply
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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Atleast tell us the reason for the delay.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I think it's due to the huge number of participants. what do you think?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

WoW!

I'm waiting.

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

Now we have record of participants, but I think for another delay we will have antirecord

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4 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Now codechef might just get a new excuse XD

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4 years ago, # |
  Vote: I like it -9 Vote: I do not like it

Its 30 minutes late. Why ?

I have to eat food..

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4 years ago, # |
  Vote: I like it +22 Vote: I do not like it

.. 87bbadf6-ba42-450c-ba38-804a04599435

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Cheers to everyone who has participated in the contest with maximum registered participants!

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

while(participants<30k): delay+=10mins

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why is the contest getting delayed??????????? I entered at 8:05pm IST to find out that the contest is starting at 8:20pm IST. When I enter at 8:20pm IST, it is showing delay of further 10 minutes!!

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    may be some question is wrong

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Maybe they're testing if the servers can handle the load

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      but that is not good idea, delaying also increases number of registrants..

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

new year resolution effect 30k

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

There should be an option for unregistration from contest if delays come.

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4 years ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

30k participants, This contest is going to be very much fun.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

please no more delay :(

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4 years ago, # |
  Vote: I like it -23 Vote: I do not like it

codeforces randi ,start krrde

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    4 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    You want me to find you on LinkedIn and send this comment to your recruiter? Delete it fast little bitch.

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      4 years ago, # ^ |
        Vote: I like it -9 Vote: I do not like it

      We often get stressed during or even before the contests, which leads to frustration. Keeping that in mind and not to forget the constant delays today i would like to appologise to absolutely nobody, do what u can , the king does what he wants.

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        4 years ago, # ^ |
          Vote: I like it +8 Vote: I do not like it

        Your frustration results in you calling this platform a "whore"? And you're no king. Just a sad pussy behind a keyboard. Don't shit where you eat. If you can't respect the platform then leave. Everybody here is "frustrated" but nobody is using these stupid insults like you.

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          4 years ago, # ^ |
            Vote: I like it -9 Vote: I do not like it

          I will not respect the platform and I'll not leave either. What can u do about it Mr. Authority?

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4 years ago, # |
  Vote: I like it +19 Vote: I do not like it

I hope this countdown is not a countdown to the next delay

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4 years ago, # |
  Vote: I like it +22 Vote: I do not like it

Come on!!!! My mom will beat me if i will not eat my dinner at time.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

They're gonna keep delaying the contest until some people unregister because of frustration :D. Don't blame them though, this is a historical milestone.

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4 years ago, # |
← Rev. 3   Vote: I like it +2 Vote: I do not like it

YES!! yEEEE! 30.000!gogogoGO! yEEEEEEEEEEES!!!!

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Me watching contest getting delayed , after waiting for 1 month for div3 - images-2021-01-24-T220338-381
upload image

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4 years ago, # |
  Vote: I like it +7 Vote: I do not like it

was the delay to hit 30k registrants lol

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4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

Now I am 16 years old.

When Contest starts, I will be 116 years old :D.

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Highest number of participants in Codeforces history.

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

If it takes so much time to reload use m1.codeforces.com , m2.codeforces.com or m3.codeforces.com.

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

Contest will be delayed for 10 mins. If it doesn't start in 10 minutes just read first sentence again.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Congratulations for having 30K coders today.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Don't delay it anymore.OK?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Mike just wants achieve 30k :D

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Number of comments increased by 200% due to this delay.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

the delay might be to get 30,000 no of participants

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4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

Meanwhile:

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

30k on codeforces round!!! Congratulations!!

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4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

RECORD! It's 30k.

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

Seems like, cp has become like engineering in India, you have to do it, whether you like it or not.

look at 30K participants

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    4 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    Thanks to indian youtubers for making this possible -_-

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Congratulations for 30k participants! This has been such a great platform.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

There we go 30000+ registrations !!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

25 mins late but... a new record :')

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

30000! Congratulations!!!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Congrats CF for 30k participants..

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Congratulations CF on achieving a new milestone of 30k participants.

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4 years ago, # |
← Rev. 4   Vote: I like it +16 Vote: I do not like it

20:04: Me to Mom: Mom, I will have dinner at 10:05.

20:05: Me to Mom: Let have dinner now; I will eat fast.

20:20: Me to Myself: Well wtf I ate so fast? Let write a comment and let the entire community know :)

20:30: Me to Myself: All the best :)

UPD:

21:00: Me: Please Codeforces, make it unrated, unable to bear queue timings :)

21:15: Regardless of rated/unrated, I stop giving the contest. #queueforces

21:20: I enjoyed the problems, will upsolve them later when the queue is not long, also Congrats on the 30k+ registration.

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

oh no! Queue of 5 min.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    How do you know the length of the queue?

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      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +7 Vote: I do not like it

      I've been waiting for 10 mintues and it's still not judged. So that's how I know.

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4 years ago, # |
← Rev. 6   Vote: I like it 0 Vote: I do not like it

TOOO LONG QUEUE uNRATED PLZ

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

o shit queue that too for this long

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

in queue "unrated"

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

please make this round unrated....very long queue timing..!!

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    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Yes, please make it unrated. The queue is of more than 20 minutes.

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4 years ago, # |
  Vote: I like it -9 Vote: I do not like it

Am I a noob king or C is actually tough.... Lol

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    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    Shut Up! You are not allowed to discuss about problems during contest.

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

make this contest unrated!

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4 years ago, # |
← Rev. 3   Vote: I like it +10 Vote: I do not like it

[Edited]

Reference: https://mirror.codeforces.com/contest/1475/status/page/70?order=BY_RELATIVE_TIME_DESC

From this page onwards for quite a few pages of submissions. (the page number will change as time goes, so a little ahead or behind, around 30 pages from the last page)

Shady activities. [Edited/]

Someone is purposely overloading the server. There are many accounts that have been created around 11 days back which have submitted codes that have lead to compilation error.

Why tho? :/

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    They may be college freshers

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Probably not, the names are spammy, all created on the same day, submitted and went offline around the same time, submitted compilation errors around the same time. Very hard for it to be freshers, the names and profiles don't look genuine.

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Make it an unrated contest please.. queues are unbearable

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

At this point they should just make this unrated, the queue is unbearable

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Codeforces is really a awesome platform

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

In div-3 no of solution submit frequency is so much.

So, If in div-3, only <1600 rating people can attend thats much better for the server i think. >=1600 rating can practice it virtually though (:

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    Most of the participants in CF are below expert or unrated so that wouldn't matter

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      and i did not said by that all problem solved but can reduce (: just my opinion sir.

      but that's 5k people submit 5k*7 solution in first hour mostly. cause they solved all before 1 hours. and initial time is most important.

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    4 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    The fact that the contest isn't rated for someone doesn't means that it cant be enjoyable on a competitive point of view

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Contest has been declared unrated!!!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why codeforces why?

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Well not just a registrants record also a queue record

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4 years ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

2021 == Extended Version of 2020 .

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    2021 == 2020 won and now it wants have some fun :)

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

30 000 participants dissapointed for the first time

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

A round of nice problemset is ruined.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

So we were trying not to annoy delays for this?!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Qᴜᴇᴜᴇғᴏʀᴄᴇs..........................................

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

to cc and cf : you either die a hero or live to become the villain

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

When CF Predictor shows +200 and the round becomes unrated...Sed lyf

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4 years ago, # |
← Rev. 3   Vote: I like it +16 Vote: I do not like it

Please consider restricting new acccounts from participating div.3 (more than $$$5500$$$ out of $$$30000$$$, two times as the number of $$$1600+$$$ people. It's really weird.) or upgrade the judge system. The number of participant is too high for the current system (or the system is a bit off today?)

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Maybe I should call it Qulayforces,right?

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

I guess, CF should only allow participants whose rating less than 1600 even to enter the problem-set page for Div 3.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    This will increase the no. of people having rating greater than 1600 to participate with a new round , which will have a big adverse effect.

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      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it 0 Vote: I do not like it

      I do understand your concern, but I guess Div3 are meant to be beginner friendly (Please correct me if I am wrong), and in such a case, why could it be only allowed to participants below 1600. (Also, If I had offended anyone, apology). I wouldn't say that high rated people shouldn't take part in lower Division contests. But given the possible scenarios of long queues and site getting down, It could be a suggestive measure.

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Suggestion is good but I think it is not practical

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Is Codeforces taking inspiration from codechef nowadays?

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    4 years ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    Never in it's lifetime will Codechef have such a huge number of participants.

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4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Queue 260 pages long :(

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I'd love to sacrifice my Internet/CPU/Screen space to see ads on this website just to have better servers. Please admin consider this way of getting better servers.

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4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

I had such a bad spree and now cf predictor showed +115 and round is unrated... brb gonna drink some bleach with vodka

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4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Very disappointing! Considering that there were 2 delays and the round was delayed by 25 minutes, it seems that they understood what was happening. Perhaps it was worth postponing the round a few days in advance, having solved the technical problems before. This is doubly sad because the tasks were interesting :(

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

They tried to prevent such unexpected issues by delaying the round a bit but still it could not be prevented :(
Anyways beautiful problem set! :D

The sad part is that today my exams got over, and I was like finally I can give the contest without much thinking about studying for exams.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Is that a coronavirus on your profile?

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      4 years ago, # ^ |
        Vote: I like it +2 Vote: I do not like it

      lol no! Its a polygon with thousand sides! That is a chiliagon!

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Getting a +150 increase and seeing contest becoming unrated hurts :(

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4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

What is the procedure in this case? Can people discuss problems already as ratings are not impacted?

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4 years ago, # |
  Vote: I like it +217 Vote: I do not like it

Sorry guys. I could not prevent the round from failing, as I was at the doctor's appointment.

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    4 years ago, # ^ |
      Vote: I like it +42 Vote: I do not like it

    Still infinite times better than Yesterdays Codechef cook-off.

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      4 years ago, # ^ |
        Vote: I like it -16 Vote: I do not like it

      But that was rated.

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        4 years ago, # ^ |
          Vote: I like it +16 Vote: I do not like it

        beside unbalanced div2 & div1,they said they have improved servers before contest , then servers didn't worked during the contest for 30 minutes , created unfair ranking gaps and then they were stubborn enough to make it rated .

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          4 years ago, # ^ |
            Vote: I like it +10 Vote: I do not like it

          Codechef is a joke nowadays. Only 2 short contests per month and that too getting server errors a lot, you can't even open IDE to submit the code forget about long judging time, similar thing happened in december as well. No wonder why CF is 10 times better than CC.

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    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    No problem MikeMirzayanov. Altough Iam sad about this round but ..... Get well Soon.

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    4 years ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    Got it. A ship was wrecked when the captain went to the doctor's.

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4 years ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

First time I solved 3 problems in a contest. But unfortunately It is now UNRATED...sad

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I was getting around 100+ rating in this contest but luck cannot favour you always :(

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4 years ago, # |
  Vote: I like it +23 Vote: I do not like it

Problem G is not available on m2.codeforces.com, which is more strange than queue problem.

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4 years ago, # |
  Vote: I like it -37 Vote: I do not like it

Remove div3 from codeforces. It was pointless idea from the beginning and as for now servers are not able to handle 30k submissions for easy problems and I don't think they will able in the near future. You're only disappointing people.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I think this is not solution

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      It is solution. Have you ever seen a queue on div1 round? Div2 rounds were unrated due to queue, as I know, but queue was caused by server issues (and extremely easy problem A and B). Today servers were on full power but anyway they weren't able to judge easy problems without queue. Removing div3 and making div2 harder will definitely solve queue issues.

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Of course we can solve problem with this for temporarily but when codeforces get bigger few years later this solution is useless

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I could bet if you were pupil, you wouldn't make this comment

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      4 years ago, # ^ |
        Vote: I like it -9 Vote: I do not like it

      What's the point of div3 round for you (and pupils)? Practice? No, you will never reach even expert if your practice consists only of div3 ABC problems. Compete? No, your CP level is too low for real competition. Competing with this level and being happy with 2000th place on contest instead of 3000th, instead of practicing, won't raise your rating and you'll be pupil for life.

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Please make it rated, I'm getting 140+ delta :) :(

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    4 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Cool, you got 140+ delta after most people left ;)

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      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      Ohh that's the reason for this miracle. I thought I done some extraordinary work today :)

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4 years ago, # |
← Rev. 2   Vote: I like it +16 Vote: I do not like it

-- Problem A, Odd Divisor

This problem asks us to check all divisors of n if there is an odd one among them. Note that the constrainst are set in a way the the simplest implementation of the factorization will go TLE. see https://cp-algorithms.com/algebra/factorization.html

Edit: Or just check if there is an divisor other than 2.

-- Problem B, New Years Number

Note that n is fairly small. So we can check all multiples of 2020, and if the difference to n is divisable by 2021. If none of them is, then ans is NO, else YES.

-- Problem C, Ball in Berland

We need to choose two pairs. So, we need to know foreach pair p1 the number of other pairs we can choose, if we have choosen p1. That number is the number of all pairs, minus the number of pairs having the one or the other member of p1 as a member.

Since each pair is distinct, we can count the frequency of all members in all pairs, and subtract that frequency from the number of all pairs.

-- Problem D, Cleaning the phone

Its a strange greedy. We can sort the applications by storage units per cost unit. So simply double the storage units of the 1-cost apps, then sort them. Then we choose the best ones until enough storage is cleaned. If not possible then ans=-1.

But, it can be that we can substitute one 2-cost app by a 1-cost app. For that, check if there is a not choosen 1-cost app that we can exchange agains the worst choosen 2-cost app, so that still enough storage is cleaned.

Not sure how to prove that there cannot be more than one such substitution.

-- Problem E, Advertising Agency

Of course we must choose the best bloggers first. But there can be equal bloggers, and if there are equal ones, we can choose among them.

Consider the number of followers of the worst of the choosen bloggers. Let cA be the number of bloggers with the same number of followers as that worst one. And cC be the number of bloggers with same followers as worst, and wich are choosen. Answer equals nCr(cA, cC). This is, because we can choose any cC of those bloggers among the cA ones.

-- Problem F, Unusual Matrix

Observe that it does not make sense to flip a row or col twice. Flip it once or not at all.

Then consider the first row. We can flip it or not-flip it. In both cases, we can see foreach column if it was flipped or not by comparing the fields of the first row of a[] and b[]. As a result we get the state of each col, flipped or not-flipped.

Then check all other rows if we can construct the b[] version of the row by using the column flips on the a[] version. If this is possible for all rows then answer is YES, else NO.

-- Problem G, Strange Beauty

We find the biggest possible set of numbers we can put into an array, then the difference to the number of all elements is ans.

Consider that we have put one number into the array. The next one must be a multiple of the first one. And then the next must be a multiple of the LCM of the first two ones... It turns out that because the last added number is allways a multiple of all numbers previously added, we can allways add each multiple of the previous number. So we can create a graph where each number has an edge to each multiple of it, then find the longest path in that graph.

Other possibility is a dp, where dp[i] is number of elements that can be added after having added element i.

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    4 years ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    Problems were really cool, thanks!

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      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +8 Vote: I do not like it

      Small note:

      A could be solved by checking if N is a power of 2 and outputing false if it is, else true

      B can also be solved by removing as many 2020s as possible, ur left with only 1s to add to the 2020s removed, if there are more 1s than 2020s removed, then its false, else true

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    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Another approach for D:

    Fix the number of 1 cost applications and binary search to find how many 2 cost you need to take

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Every time I will forget that we can construct an algorithm with time complexity O(n + n/2 + n/3 + .......n/n).

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    I have tried D with the same approach but it is not working can you tell me my mistake here is the link to my submission https://mirror.codeforces.com/contest/1475/submission/105410745 This approach is similar to spookywooky

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Video Tutorial A and B:https://www.youtube.com/watch?v=vMpkqoZZN0I

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    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    I don't see a single submission from your handle, why should one trust your solutions?

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4 years ago, # |
  Vote: I like it +75 Vote: I do not like it

I was wondering how that person was able to solve an problem C and problem E and problem G in one minute???

problem A in minute 4

problem B in minute 5

problems C & E & G in minute 6???

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4 years ago, # |
  Vote: I like it +7 Vote: I do not like it

No matter the round is unrated, the problemset was really good. Thanks for making div3 rounds "for div3 participants."

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Don't say something generally! yes, it mattered for me and for many users

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4 years ago, # |
  Vote: I like it +19 Vote: I do not like it

Am I the only one who reduced F to a 2-SAT problem?

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    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    Can you please explain your 2-sat solution. Thanks in Advance!

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      4 years ago, # ^ |
      ← Rev. 6   Vote: I like it +3 Vote: I do not like it

      Let's say $$$r_{i}$$$ is true if we do horizontal xor on ith row. Similarly define $$$c_{j}$$$ for jth column.

      if ($$$a[i][j]$$$ and $$$b[i][j]$$$ are equal) it must be the case that either (both $$$r_{i}$$$ and $$$c_{j}$$$ is true) or (both $$$r_{i}$$$ and $$$c_{j}$$$ is false). Here we can add one edge (undirected) between $$$\neg r_{i}$$$ and $$$c_{j}$$$ and one edge (undirected) between $$$r_{i}$$$ and $$$\neg c_{j}$$$.

      if ($$$a[i][j]$$$ and $$$b[i][j]$$$ are not equal) it must be the case that either ($$$r_{i}$$$ = true and $$$c_{j}$$$ = false) or ($$$r_{i}$$$ = false and $$$c_{j}$$$ = true). Here we can add one edge (undirected) between $$$r_{i}$$$ and $$$c_{j}$$$ and one edge (undirected) between $$$\neg r_{i}$$$ and $$$\neg c_{j}$$$.

      Now this is like 2-Sat on an undirected graph, if a solution exists then $$$i$$$ and $$$\neg i$$$ must not belong to the same component. I used Union Find to check this

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        4 years ago, # ^ |
          Vote: I like it +5 Vote: I do not like it

        Brilliant solution. Thanks a lot for the explanation!

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Problem E was quite easy ... probably somewhat problem C level.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    And D was harder than G and F

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Can you please help me in finding out where my logic for D is failing its giving wa on testcase 3

      My logic -> Binary search on answer and for each mid(convience value) choose greedily between 1 and 2 for different partitions...

      Link to my solution.

      Any sort of help is highly appreciated...thanx!

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4 years ago, # |
  Vote: I like it +14 Vote: I do not like it

Could someone explain this:
I can't believe that there exists a man who can solve 3 different problems(including the most difficult one) within 1 minutes. Although this round is unrated, such behaviors may violate the rules?

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    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    It is impossible to solve these 3 problems within 6 minutes without knowing the problem beforehand as I don't think these 3 problems were one-liners

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      4 years ago, # ^ |
        Vote: I like it +11 Vote: I do not like it

      Strong as Tourist has spent 12 minutes to solve them... What is more, I think this participant didn't know the problem before the contest started because I really trust Codeforces that it wouldn't allow problems leaked. It may be the result of group cooperation.

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4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Any idea how to fix TLE on test-12 in problem G TLE_CODE

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    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Precompute the factors for 1 to 200000 outside your solve loop, rather than calculating them every time

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +5 Vote: I do not like it

    use array instead of map.since numbers are from 1 to 2*10^5 you can use array.

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    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    Here you go

    1. Precompute all the factors in $$$O(A \log A)$$$.
    2. gp_hash_table without passing custom_hash is just as slow as unordered_set.

    Here, it would just be faster to make a dp array and clear it everytime since the number of testcases is small. Even in the case where the number of testcases were large, you could selectively clear those indices which we used.

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it
    • Test case 11 — 1.5s
    • Test case 12 — TLE 5s

    I really wonder what is test case 12

    105411878

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

for problem E , my logic was, store frequency of each follower count and greedily select the bloggers with high frequency : in each step we see if the number of bloggers will exactly fit necessary number or less than required (in this case we just select them ,only 1 way) or more than required number (select required from available with that freq. my submission the combinatorics part is from galen colins library. please check

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4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

I have a weird solution for F. It is to check whether for every 2x2 submatrix, number of ones in matrix A and B must be even (for the same 2x2 submatrix). Is there a proof why it worked?

105379848

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    4 years ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    Some dumb reductions first.

    Note that the order of flipping doesn't matter, there's no point in flipping the same row/columb twice. Take the xor of the two grids, now we need to check if the resultant grid (call this $$$x_{i, j}$$$) is reachable from the grid filled with zeroes.

    Let $$$S_i$$$ be $$$1$$$ if we flipped the column $$$i$$$, $$$0$$$ otherwise; similarly define $$$T_j$$$ for rows. We see that $$$x_{i, j} = S_i \oplus T_j$$$. (You can get a solution from here by first setting $$$T_0 = 0$$$, then finding all $$$S_i$$$ and $$$T_j$$$ from the relations and finally checking if all the values are consistent.)

    So, for any two-by-two grid we have $$$x_{i, j} \oplus x_{i, j + 1} \oplus x_{i + 1, j} \oplus x_{i + 1, j + 1} = (S_{i} \oplus T_{j}) \oplus (S_{i} \oplus T_{j + 1}) \oplus (S_{i} \oplus T_{j}) \oplus (S_{i + 1} \oplus T_{j}) \oplus (S_{i + 1} \oplus T_{j + 1}) = 0$$$.

    This gives the necessity of the check, to prove that its sufficient we give an explicit construction of $$$S$$$ and $$$T$$$ which works, $$$S_i = x_{i, 0}$$$, $$$T_j = x_{0, 0} \oplus x_{0, j}$$$.

    Induct on $$$a, b$$$ to show that $$$x_{i, j} \oplus x_{i, j + a} \oplus x_{i + b, j} \oplus x_{i + a, j + b} = 0$$$ (basically the xor of the endpoints of any rectangle is $$$0$$$). In particular, $$$x_{a, b} = x_{a, 0} \oplus x_{0, b} \oplus x_{0, 0} = S_a \oplus T_b$$$ as required.

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4 years ago, # |
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Can someone help me in problem D? Why my code is giving Exit code is -1073741819 (RTE)? What does that exit code .... means? https://mirror.codeforces.com/contest/1475/submission/105404284

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4 years ago, # |
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I am getting runtime error on test 2 of problem d..can anyone please provide some tc to make me understand what is the problem ..

https://mirror.codeforces.com/contest/1475/submission/105385557

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4 years ago, # |
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Check out my explanations of problem F and G — solution

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4 years ago, # |
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Anyone want to increase their hack count??

Here you go... :)

105318690

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4 years ago, # |
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Can anyone help me in uninitialized value usage error, I don't know why I get this error. https://mirror.codeforces.com/contest/1475/submission/105411235

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4 years ago, # |
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For F I use some greedy solution and can't prove it. Can somebody says why this works? 105382873

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4 years ago, # |
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for problem C it never specifically stated that pair cant be repeated, doesnt that mean the i can use that as a test case in hacks?

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    4 years ago, # ^ |
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    Actually stated It is guaranteed that each pair is specified at most once in one test case.

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      4 years ago, # ^ |
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      oh, my B didn't notice that. you're a real G

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4 years ago, # |
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Hello, can someone explain to me Problem G : why this sample of test 2 5 2 1 5 5 4 answer = 2

Isn't removing 5 is enough to meet the required conditions?

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4 years ago, # |
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One user seems to have solved 6 problems in 6 minutes, but later all of their submissions were tagged as skipped. I was just wondering if this was just a tester or a cheater? If it was a cheater, then obviously you had some kind of a leak.

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4 years ago, # |
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Can E be solve by dp. Like we know the maximum followers we can get. And then by dp we can find ,the no. of sequence having k bloggers that has sum equal to max sum. I have tried liked this but getting wrong answer.

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    4 years ago, # ^ |
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    Yes, it's pretty easy with dp. You can use dp[i][j] with the meaning:

    • dp[i][j].first — maximum sum if you choose a subset of j people from the first i
    • dp[i][j].second — the number of different ways to get that maximum sum with j people chosen from the first i.

    The answer will be dp[n][k].second. The transitions are also pretty standard(for every person i you can either take it or not in the solution). You can check my solution for more details: https://mirror.codeforces.com/contest/1475/submission/105385888

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4 years ago, # |
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I cannot see the problem G in m1.codeforces.com in the past contest:(

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4 years ago, # |
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I am very angry about the fact that 1475F - Unusual Matrix is included in the set. What am I supposed to learn from adhoc problems???

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4 years ago, # |
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Hello everyone, I can't solve problem A using a trivial algorithm. The program just prints NO for every testcase. Can any people tell why?? Here is my code: 105509143

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    4 years ago, # ^ |
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    You can't check just the numbers smaller than sqrt(n). For example, n=26 would fail for your test because it would check only if 26 is divisible by 3 or 5, which it isn't.

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      4 years ago, # ^ |
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      Thank you very much! One more question: Isn't it true that all factors of a number n less than or equals to sqrt(N)? That was why I didn't check them all.....

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        4 years ago, # ^ |
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        Only about half of them are smaller than sqrt(n)! Take a number i for example, if n is divisible by i, and n/i=k, then n is also divisible by k and n/k=i. But if all of the divisors were smaller than sqrt(n), then both k and i would be smaller than sqrt(n), and k*i would have to be smaller than n, where we get a contradiction! Your algorithm also has to go through all numbers i from 2 to sqrt(n) inclusive, and then if n is divisible by i, check if any of i and n/i is odd.

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4 years ago, # |
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I was so close to finally reach specialist, I had a +219 delta... I guess I'll never reach cyan

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4 years ago, # |
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Can anyone tell why this is wrong (question g). 106012046

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