Intel Code Challenge Elimination Round will take place on Saturday, 1 October 17:05 MSK. Only russian citizens from 18 to 27 years old can officially participate in this competition.

However, for all other users of the Codeforces it will be an usual round. The round will be rated and both divisions can participate.

There will be 6 problems and 2 hours to solve them. Scoring distribution will be announced closer to the start of the round.

The problems were prepared by me — Vladislav Epifanov (vepifanov). I want to say thanks to Alexey Shmelev (ashmelev), Alexander Fetisov (AlexFetisov) and Vladislav Isenbaev (winger) for testing the problems, coordinator of the Codeforces Gleb Evstropov (GlebsHP) for his help with the contest preparation, and Mike Mirzayanov (MikeMirzayanov) for the Codeforces and Polygon systems.

UPD. Scoring: 500-500-1000-1500-2000-2500.

UPD 2.

I must apologies for the problem C. We decided to simplify it in the last moment, and it turned out, that the simplified version of it already appeared on another online judge.

Anyway, I hope that the second round will be better than the first one.

Editorial for this round will be published on Sunday, 2 October.

UPD 3. Editorial

Hello, Codeforces!

30th September 2016 at 17:05 MSK Codeforces Round #374 (Div. 2) will take place for second division participants. Traditionally, participants from the first division will be able to join out of competition. Please, notice that the start time is unusual.

This is my second Codeforces round, I tried to make problems interesting for everyone, so I recommend to read all problems statements! I hope that everyone will find something new and interesting. I wish lots of accepted runs and higher rating to all participants.

I want to thank Michael MikeMirzayanov Mirzayanov for wonderful platforms Polygon and Codeforces, and for help in preparing the problems, my best friends Danil danilka.pro Sagunov also for help in preparing the round and Ivan BledDest Androsov for testing the problems.

Participants will be given five tasks and two hours for solve them. Scoring system will be announced traditionally closer to round start. :)

The scoring is almost the standard: 500-1000-1500-2000-2750

UPD: Editorial

Welcome to 2016-2017 CT S03E04: Codeforces Trainings Season 3 Episode 4. The training duration is 4.30 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be available as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

Visit Codeforces::Gym to find the contest and register.

We are planning to start on September, 28, 2016 13:10 (UTC).

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

Good luck!

Hello everyone,

Several people are asking me when A2 Online Judge is coming back, and unfortunately the issue this time might take longer to fix it.

This is the server which was hosting the website in my garage for several years:

And I think it's time to move to the cloud, but this requires some money. I created a campaign to raise $3000 which I need to host it on AWS for the next 3 years at least. You can read more details here: https://www.gofundme.com/support-a2oj

Please support to bring the website back, even if by just sharing the campaign.

Thanks in advance,

Ahmed Aly

Hi everyone!

Codeforces Round #373 (Div. 1 + Div. 2) will take place on 23 September 2016 at 16:05 MSK. Please note that the timing is unusual.

This time tasks for you were prepared by me (Matvey Aslandukov) and my brother _XuMuk_ (Andrew Aslandukov). It is our first codeforces round and we hope you'll enjoy it. We want to say special thanks to Seyaua (Ievgen Soboliev), AlexFetisov (Alexandr Fetisov) and winger (Vladislav Isenbaev) for testing the problems, GlebsHP for his help with the contest preparation, and MikeMirzayanov for the excellent platforms Polygon and Codeforces.

Coincidentally, the date of the round falls on my birthday, so I am very happy that I can spend that day surrounded by our friendly community :)

There will be five problems and two hours to solve them. Traditionally, the scoring distribution will be announced later.

Good luck!

UPD1:

Scoring:

Div. 2 : 500 1000 1500 2250 2250

Div. 1 : 500 1250 1250 2000 2500

The problems are sorted by difficulty but as always it's recommended to read all the problems.

UPD2:

Contest complete! Thank you all for participating :)

Unfortunately, as noted Um_nik, many solutions of div.1 B task, including the author's, were incorrect. Now we are working on this problem. If we still manage to find the right solution and answers on pretests will be the same, the round may be rated. Otherwise, it will be unrated.

Thus final results significantly delayed. We apologize for the situation. If you have thought about the correct solution — write to us.

UPD3:

We made a decision to start system testing with the current solutions and tests. The question will be round either rated or not is still opened.

UPD4:

After considering different option and estimating their pros and cons, Codeforces team decided that the main factor to make a decision on whether the round should be rated or not is how much the bug affected the results.

In the second division, only two participants managed to implement the correct greedy algorithm for the original incorrect version of the problem D, thus we consider the effect of this problem on the final standing to be negligible. The contest for division two will be rated.

Things are very different for division one, as there were plenty submission to problem B and problems B and C took the most part of participants worktime during the contest. Assuming this fact we suppose that this bug affected the final results a lot and there is no way to consider its influence on each particular participant. As a result, the contest for division one will be unrated.

The only thing left to do is to apologize to the participants. We will do our best to avoid such situations in the future.

UPD5:

Congratulations to the winners!

Div.1:

1. enot110
2. Egor
3. KrK
4. UsedToBe
5. IvL

Div.2:

1. Adenium_Rose_Of_Desert
2. GS_ZJ_137
3. haqkux201
4. MemoryLimitExceeded
5. immortalCO

Editorial is ready!

I know what is the problem

Where we are going we need all the courage we can get

When I first read the comment that our shiny new gcc 6.2 C++14 compiler has slow printf and scanf I immediately knew what I would do the next weekend. The new MinGW switched to custom implementation and I didn't need anything else to tell what the problem is. Of course, their format string parsing is too slow, they copy data around countless times, no file buffering is used and they have enough levels of indirection to make finding the real code feeling like a treasure hunt. What else could be the problem after all?

Keeping this thoughts in mind I patiently waited for a weekend. When I finally opened MinGW source and searched for printf function, I was pleasantly surprised. The real implementation was only a couple hops away and soon enough I was looking at the heart of printf code. MinGW did try to conceal it a bit though by naming it mingw_pformat.c. But a ~100Kb source file was a very clear hint where all the action is. The format string parsing was straightforward and located in a single big function. Everything was passed by pointer and there were hardly any levels of indirection. But the data was clear — MinGW printf is twice as slow for integer numbers compared with msvcrt.dll and scanf is even worse. Increasing the file buffer size didn't help at all. Reluctantly, I had to admit that the problem is somewhere else. But what could possibly be the problem?

Welcome to 2016-2017 CT S03E03: Codeforces Trainings Season 3 Episode 3 - 2007-2008 ACM-ICPC, Central European Regional Contest 2007 (CERC 07). The training duration is 4.30 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be available as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

We are planning to start on September, 21, 2016 13:10 (UTC).

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

Good luck!