Good afternoon!

The round duration is increased to 2 hours and 30 minutes.

Hello!

As many of you have noticed we have new features on Codeforces. The tab “Friends” has appeared on the user ratings page. But it is only the first of improvements made. Now you can view a list of friends on problemset standings, contest registrants and contribution standings pages. Because of increasing popularity of Codeforces the pagination has been added to the rating page.

But that's not all. In order to classify problems, it was decided to introduce the ability to add tags to them. Search by tags is not implemented yet, but administrators and users with high (your color should be at least blue) rating can add tags right now. To do this, simply open the desired problem and add tags in the sidebar form.

As you can see, the project development is actively underway. We would like to hear from you new constructive suggestions. 

Updated:

In the near future will be implemented a compact view of tags in the problemset and a setting to show/hide tags.

Maxim Shipko, Codeforces Team

The coding phase has been finished. Please wait for the final testing and results.

Good day everybody.

Everything written below is not a April Fool's joke. Though it is also a funny occasion :)

We are glad to announce a new experimental contest on Codeforces, "Problem Parser Contest".

Have you ever made training sessions, using the previous contests' archives? Have you downloaded from the Internet contest archives to test for your solutions locally? If the answer is 'yes', then you couldn't help noticing that each organizer insists upon inventing his own way (format) to distribute problems. Yes, it is true!

I've prepared and organized a huge number of trainings based on the previous contests. It is often rather a monotonous task; one often has to write some scripts that rename the input/output files of the problem into the standard form. In archives they are called very differently: they can be river.in.1, river.out.1, river.in.2, river.out.2, etc. In another problem they can be tests/1.dat, tests/1.ans, tests/2.dat, tests/2.ans etc.

At some point I got fed up with it and wrote a script that told the patterns of paths to the test files, using some heuristics and the regularity I'd noticed. The script worked well, but it wasn't perfect.

Hello everyone!

I am an author of today problemset. It is my second round on Codeforces. I hope you will like this round like my first one:)

Good luck!

UPD
Winner is unicef.
Editorial.

Unusual tournament Manthan 2011 showed the weaknesses of the current rating formulas. After the end of contest the winner of the competition tourist has expected rating change equal to "-1":)

This has arisen due to reduction of the calculated changes in such a way, that total sum is equal to 0. That is, Gennady was in some pros before such changes, but as the sum of all the changes turned out to be positive, then all the ratings were a little reduced. As a quick dirty hack in the round I turned off this feature, leading to a one-time inflation. Even a small mistake: I noticed that participants in the second division get too many points after a good performance on "Div. 2 Only" rounds.

I'm glad to see you on Codeforces Beta Round # 64.

Today I am the author of the tasks. I'm a student of Tyumen State University.

I want to thank all those who helped me to prepare the round: Nikita Durynin (Austeritas) for the pair ideas for the tasks, Dmitry Bochkarev (Walrus) and Chernenkov Alexey (Laise) for the testing, Artem Rakhov (RAD) for coordinating the activities, Maria Belova for translating and Mike Mirzayanov (MikeMirzayanov) for a great system.

Today you will visit the Walrusland and help the common citizens and government to solve their problems.

Good luck for everybody, let the best man win!

Winner is Petr. Congratulations!

Analysis

Hello!

Today I am the author of all tasks. At the contest you will be asked to help students from Chelyabinsk in solving their non-trivial problems.

I want to thank all those who helped me to prepare the round: Anton Garder for his invaluable assistance in the preparation of sets of tasks, Demid Kucherenko for assistance in the preparation of conditions, Artem Rakhov for coordinating the activities and patience J, Maria Belova for translating and  Mike Mirzayanov for a great system.

 Good luck!

Winner - Solo

Analysis - http://mirror.codeforces.com/blog/entry/1571

Hi all!

Unknown language round #1 was up, 21st of February and now we're going to hold yet another Unknown language round.

It will be the usual ACM-ICPC unrated contest , so there is no hacking! The only feature - you will be able to submit problems using the only one, not very popular language. What? It's a secret! And I expect you'll have to learn the language at the time of contest since the used language will be a secret until ~1 minute before the start of contest.

Problem setters of this round are Alireza Farhadi, Saeed Ilchi, Sajjad Ghahramanpour, Zahra Rohanifar and Me. We are extremely grateful to Mike Mirzayanov and Artem Rakhov.

Number of problems will be more than usual and the problems concentrate on coding abilities rather than algorithmic view and problem solving techniques.

UPD:The contest is over

Congratulations to the top 3 winners who solved all problems:

Wrong

tomek

watashi