Hi all,

I was honored to open the fourth hundred of Codeforces Rounds. Unfornunately, neither I nor my friends couldn't invent any hard problems, so it's only a Div. 2 Round. But we'll definitely prepare a full round in the future! As always, I thank Zlobober for his help in preparing the problems, Delinur for English translations and MikeMirzayanov for the Codeforces itself.

The problems must be pretty easy for Div. 1 guys, so let's start a challenge: reds should solve everything in 30 minutes, yellows — in 1 hour, and violets — in 1 hour and a half. How many people will be able to make a success?

The score distribution will be standard. Wish you accepted solutions and successful hacks!

UPD 1. Congratulations to the winners in Div. 2:

1. PauGra
2. cuvwqe496
3. tgehr

and in Div. 1:

1. niyaznigmatul
2. I_love_Tanya_Romanova
3. dreamoon_love_AA

UPD 2. This is the editorial: /blog/entry/17643.

Hello, Codeforces!

On Sunday, April 26th at 19:00 MSK the 300'th regular Codeforces Round will take place.

I would like to congratulate all Codeforces members and administration on this remarkable milestone. The platform has grown hugely in size and quality since its foundation, has hosted lots of exciting competitions, and has been providing the opportunity to everyone to hone their problem solving and algorithmic mastery. For this we thank the Codeforces platform creator MikeMirzayanov and all the Codeforces crew. Keep up the incredible job, guys!

That being said, I'm excited to announce that the problems on the jubilee three-hundredth Codeforces Round will be set by me, Mikhail Tikhomirov (Endagorion). You may remember the past rounds with my problems: #99, #109, #265, #283, and (in part) #295. I thank the Codeforces problems coordinator Max Akhmedov (Zlobober) for helping me in preparing this round, and Maria Belova Delinur for translating the statements in English. Also, special gratitude to Vladislav Isenbaev (winger), Alex Fetisov (AlexFetisov) and Pavel Kunyavskiy (PavelKunyavskiy) for testing the problemset and help with preparation.

This round will be shared for both divisions and will last two hours and a half (as you can see at the Contests page). The round will feature several ( ≥ 6) problems, varying in difficulty and topics involved. I hope that everyone will find an interesting and satisfying problem just for themselves! The scoring will be announced later.

To add up to the excitement, there are 30 exclusive Codeforces T-shirts to compete for in this round! The top 15 participants will get their T-shirts right away; another 15 will be randomly distributed among those who place in the top 300. Even if you think your chances on being the very best are weak, there are still good odds you will get a treat! =)

That's it. Mark your calendars and come back to compete for the prizes and for the fun!

UPD: there will be 8 problems. The scoring is standard (i.e. not dynamic): 500-1000-1500-1500-2000-2500-3000-3000.

UPD2. In order to choose people getting T-Shirts we will use the following python3.4 code that you can manually run in "custom invocation" tab on Codeforces. It uses an integer as a seed for random generator, this integer should be equal to the last submission number that happened during the contest.

import random
seed = int(input())
rnd = random.Random(seed)
# all contestants except top-15
contestants = list(range(16, 301))
rnd.shuffle(contestants)
tshirts = list(range(1, 16)) + contestants[:15]
for x in sorted(tshirts):
    print(x)

UPD3: Thanks for participating!

The winners are:

1. bmerry
2. Egor
3. Petr
4. rng_58
5. scott_wu
6. jqdai0815
7. eatmore
8. atetubou
9. qwerty787788
10. niyaznigmatul

The list of places getting the T-shirts are 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 40 46 67 75 80 102 103 144 152 161 169 198 233 243 269. The lucky participants are as follows: bmerry, Egor, Petr, rng_58, scott_wu, jqdai0815, eatmore, atetubou, qwerty787788, niyaznigmatul, gs12117, W4yneb0t, JoeyWheeler, zxqfl, yeputons, kcm1700 & HYPERHYPERHYPERCUBELOVER (sharing the 40-th place, so both get a T-shirt), piob, Leo_Yu, matrix & Nerevar (sharing the 75-th place), Haghani, ACube, DemiGuo, etal, Emarci15, hlwt, Salvare001, dzy97, FatalEagle, gchebanov & Jimanbanashi (sharing the 243-rd place), and Solaris (please let me know about any mistakes). Congratulations!

UPD4: At long last, the editorial is up! Enjoy, and sorry for the waiting.

April 18, 18:00 (UTC) the second Wild-card round of VK Cup 2015 will take place.

Participants are invited to achieve progress in solving an unusual problem. VK Cup teams which were advanced to the Round 2 (and didn't advance to the Round 3) will take part in VK Cup 2015 - Wild Card Round 2 officially. In addition, this round will be open to the public for unofficial participation for everybody. Registration will be open for the whole round duration.

The round will be one week long. After the end latest submission (with positive score) of each participant will be judged on system tests.

Good luck!

UPD.: System testing is done. Final tests are available by link: http://assets.codeforces.com/files/vkcup-2015-wildcard-2-tests.2.zip

You can appeal on tests and their answers until April, 28th, 23:59:59. After that we will finalize the results. After finalizing all found bugs will not affect the final standings.

This Friday, April 17th, 19:00 there will be Round 2 of VK Cup 2015! For all unofficial participants there will be an online mirror that is a usual rated div1-round. Any div1 contestant that does not participate in official Round 2 is able to compete in this mirror.

Round consists of 6 problems that are shuffled randomly. There will be a smooth dynamic scoring system.

Round is brought to you by Codeforces team, VK team and user Errichto, that offered his important help as a part of his donation for "Codeforces 5 years campaign". Significant testing effort was made by user winger.

Good luck and have fun!

UPD: Thanks everybody for participating! Editorial has just appeared. See you on Wild-card Round 2 and mirror of Round 3!

Hi.

Codeforces round #299 is gonna take place soon(exact time) and I'm the writer. I'm lucky to be the first Iranian author in Codeforces, in your and our new year (2015 and 1394).

Now, I wanna thank: myself(PrinceOfPersia) for writing the problems(:P), MikeMirzayanov for great Codeforces and Polygon platform, Zlobober and Damon and sobhan.miryoosefi for helping me prepare this round, Haghani and SoroushE for testing this round, Delinur for translating problem statements into Russian and big thanks to my great buddy, HosseinYousefi for problem legends and the pictures.

Also, I wanna thank MinakoKojima for teaching me how to use polygon and testlib and so much other things about it (about a year ago).

This is my first official contest(after all those contests in Gym :D). I hope you enjoy it.

The main character of all problems is Tavas, well-known by eating CoffeeMix without water! Trust me, when he does that it smells awful.

Also, you'll meet his friends.

I hope you enjoy the problems. I wish you all high ratings, many Accepted solutions and Successful hacking attempts. And Hacked instead of Failed System Test.

Scoring will be posted later.

GL & HF ;)

UPD: Scoring will be standard for both divisions (500-1000-1500-2000-2500).

UPD2: Contest is over. We're waiting for system testing. Editorial is published.

UPD3: System test is done. Congratulations to all winners.

Div.1 winners:

1. jcvb
2. rng_58
3. vepifanov
4. mmaxio
5. flydutchman

And Div.2 winners are:

1. l1n4r
2. 0e352a
3. vintage_Vlad_Makeev
4. wilcot
5. boray

Good job everyone, see you ;)

Hello, Codeforces!

I'd like to invite you to Codeforces Round #298 (Div. 2). It will be held on Sunday, April 12 at 19:00 MSK and Div. 1 participants are invited to join out of competition.

Problems have been prepared by Maxim Mescheryakov (Neon) and Danil Sagunov (danilka.pro). We hope you'll find them interesting.

Great thanks to Maxim Akhmedov (Zlobober) for helping us preparing the contest, to Maria Belova (Delinur) for translating the statements into English, to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon systems and ideas of some problems. Also thanks Vitaliy Aksenov (Aksenov239) for writing solutions.

You will be given six problems and two and the half hours to solve them.

UPD: Scoring system 500-1000-1500-2000-2500-3000

UPD2: Competition completed! Thank you all!

UPD3: Congratulations to the winners!

1. xuanhien070594

2. misis

3. Mikagura_Seisa

4. plem

5. 11111111

UPD4: Editorial here

Hello Codeforces.

This is a really good and pleasant day for us. We are happy to announce that the fundraising campaign on Codeforces is successfully completed and its results are even beyond our expectations. Thank you for your support, your trust and your kind words.

By the way, we have some more unprocessed PayPal transfers: for unknown reasons the notifications in some cases didn't contain some data needed to process them automatically. We will process them manually and update the data as soon as possible.

To all of you waiting for our present in the mailbox, please update your Codeforces profile information or make sure that it already is complete and up-to-date.

Thanks!
Mike Mirzayanov