By MikeMirzayanov, 6 years ago, translation, In English,

The ACM-ICPC Northeastern European Regional Contest 2011 is over. Congratulations to the winners! I especially want to mention the team that will represent our region on the World Finals in Warsaw:

  1. SPb NRU ITMO 1 (Kapun, Kever, Nigmatullin) — 1-st place, champions
  2. Moscow SU 1 (Fedorov, Kaluzhin, Rogulenko) — 2-nd place
  3. Belarusian SU 1 (Bahdanau, Pisarchyk, Sobol) — 3-rd place
  4. Saratov SU 2 (Ivanov, Kuznetsov, Rakhov)
  5. SPb SU 1 (Andreev, Boykiy, Fondaratov)
  6. Moscow IPT 1 (Dlugach, Gimadeev, Shishkin)
  7. Ural FU 1 (Dolgorukov, Schelkonogov, Soboleva)
  8. Altai STU 1 (Silin, Uvarov, Yesipenko)
  9. Ufa SATU (Lezhankin, Mazgarov, Ripatti)
  10. Nizhny Novgorod SU (Lyulkov, Shmelev, Vadimov)
  11. Belarus SUIR 2 (Berezhnov, Brukau, Ropan)
  12. Udmurt SU (Abizyaev, Kibardin, Urbanovich)
  13. Latvian U 2 (Kalinicenko, Vihrovs, Vilcins)
  14. Kazakh-British TU 3 (Aitbayev, Satylkhanov, Almakhan)
  15. Tomsk SU 1 (Chadnov, Kolupaev, Afanasev)
  16. Volgograd STU (Agafonov, Chalyshev, Zhorin)

Codeforces wishes all future World Finals participants the success in preparing for the competition and good results in the final!

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By MikeMirzayanov, 6 years ago, translation, In English,


On Friday, November 25 at 19:00 I'm waiting you on the Codeforces Beta Round #95 (Div. 2). This round is prepared by me. It is not easy to prepare a round, but it is always useful and interesting. By my example, I want to hint to top participants that rounds of famous people — it's always interesting!

Apart from me RAD, Nickolas and Delinur were doing work on the round. Moreover, homo_sapiens still do not know, but very soon I will ask him to solve this round as a tester:)

It will be unusual round because you will find six problems. It's a little experiment — I hope that it will help each participant to find interesting problems to themselves.

I believe that the out-of-competition participants from Div.1 will have some fun solving the round.

The problem scoring is: A - 500, B - 1000, C - 1500, D - 2000, E - 2500 and F - 2500.

Good luck!


UPD. The competition has ended. Here are the results. First place was taken by the representative of China — liuq901. Congrats! It was nice to see such interest to the contest. Thank you for your participation!

Unfortunately, I do not have the opportunity to write a tutorial. If you deal with it I will be grateful.

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By Nickolas, 6 years ago, translation, In English,

So here goes an editorial for the round. For me Befunge is one of the languages in which it's much easier to write code than to read it (and debugging code written by someone else is a complete torture; that's why we don't have hacking in ULRs). That's why I'll post just the general idea of the solution and my own codes — the latter just to show that I can code in Befunge too.

A. Hexagonal numbers


A "consolation" problem, which requires only to understand the principles of working with stack. Read n, duplicate it, multiply the topmost copy by 2 and decrement the result. Now the stack contains two numbers n and 2n - 1; multiply them and print the result.

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By Nickolas, 6 years ago, translation, In English,

The round is over; I hope you enjoyed it. Here is the editorial.

The language of this round is Befunge, a lovely two-dimensional esoteric language. It's quite neat and convenient, especially for an esoteric language. Thus, for example, "A+B" problem, where A and B are given in separate lines, can be solved like this:


To learn the language you can read the original documentation (the rumor is that it is broken in some browsers), examples of programs at Rosetta Code and Progopedia article with annotated examples.

Our testing system uses befungee interpreter, which implements Befunge-93 dialect. To run the interpreter, one needs to have Python installed (version 2.6 or so, but not 3.*). Download files, and to the directory with your programs and run the interpreter with python <Befunge program name> command. Note the built-in debugger (run with --debug --delay=100 option) which allows to watch the movement of instruction pointer through the program and the effect it has on the stack.

As an alternative local IDE you can use WASABI which requires Java. Download interpreter arhive, unzip it and run with java -jar "Wasabi v1_4.jar" <Befunge program name> command.

In input data end of line is marked with #10 character (you'll need this for problems which require reading the string till the end of line). Your program's return is checked to be accurate within the whitespace and line feeds; it's not necessary to end the printed lines with line feeds, and if a problem requires printing several numbers, they can be separated with any number of spaces. Extra spaces at the end of line are also allowed.

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Announcement of Unknown Language Round #4
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By Sammarize, 6 years ago, translation, In English,

Hello everyone!

I am glad to welcome you on Codeforces Beta Round 94. I hope, some more early time of start will not have bad effect on you results =) 

I'm author of today problems. I'm a graduated student of SPbSU, Valery Samojlov. This is my second round. I hope, today nobody will be sorry of his participation. I want to say very big thanks to RAD, who rend me very big support with preparation of problems. Also thanks to Maria Belova, who has translate statements to English.

Please, don't be startled of unusually cost of problems:

Div-1: 1000 - 1500 - 1500 - 2000 - 2500

Div-2: 500 - 1000 - 2000 - 2500 - 2500

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By Ripatti, 6 years ago, translation, In English,

Hello everyone!

I am glad to welcome you on today round of Codeforces. I hope that recent color revolution and a more later time for start of round will make some variety into process of solving problems:)

An author of today problems is me. RAD helped me to prepare this round, Delinur translated statements into English.

Good luck.


The round ended, ratings was updated.

Winners of div1:

1. Egor

2. tourist

3. unicef

4. sevenkplus

5. ivan.popelyshev

Winners of div2:

1. RainbowDash

2. cjtoribio

3. miraliv

4. adrianoo

5. majia5



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By RAD, 6 years ago, translation, In English,

Unfortunately, Codeforces Beta Round #93 is rescheduled for tomorrow because of circumstances beyond our control. The new time is November, 9, 21:00 Moscow time (exactly 24 hours ahead).

We apologize for any inconvenience.
See you tomorrow,

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By Nickolas, 6 years ago, translation, In English,

Every time I win a trip to any kind of tournament onsites (so far this happened three times, so I can generalize), I find myself facing a serious problem, named "souvenirs". I've settled this question once and for all as long as it concerns myself: the best souvenir is a pile of photos accompanied by a thrilling story. The second-best is a couple of Swiss chocolates, though I can handle both at the same time :-) But one can't live in a society and be free of it; and it's the souvenirs for people around me that become a real problem.

Take, for example, my last year's trip to Las Vegas. I went there with a t-shirt demand from my future husband's sister. Besides, my future husband himself stayed at home (his visa application was unexpectedly refused, and there's not much point in winning a trip without the visa), and I felt I had to bring him something to cheer him up. So my shopping plans were quite intense.

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By MikeMirzayanov, 6 years ago, translation, In English,


Today is November 7th. And this, as you probably know, is a very special day for many ex-USSR citizens. Many years ago on this day the Great October Socialist Revolution happened. I still remember red flags and military equipment on the avenue and the feeling of common joy and holiday. But today, in 2011, we have another revolution — the Codeforces revolution of colors and titles. Hooray!

So, over the last few months our community has grown significantly. If we count the users who have participated in the rated contests over the last 9 months at least once, at the beginning of the year they were 4330, and now — 7615. This is a great step forward! Of course, this leads to a dramatic rating inflation. Most of the ELO-like ratings have the same issue. For example, only A. Karpov had Elo chess rating of more than 2700 in 1979; however, there were as much as 15 people with such rating in 1994, and in 2009 they were 33. In 2001 there were less than 10 red players on TopCoder; in 2005 they were about a hundred and now — more than 250.

A similar effect occurred on Codeforces. It is particularly striking as it is accompanied by a marked audience growth. For this reason it was decided to change the color system . In addition, the record shows that not all participants liked the military ranks. Besides, they are quite far from our intellectual and sporting spirit. Today we will disband Codeforces as a military unit and introduce sport titles. We've mostly used the titles from intellectual sport games to work out the following classification:

Ratings Range Color Title Division
2600+ Red International grandmaster 1
2200 - 2599 red Grandmaster 1
2050 - 2199 Orange International master 1
1900 - 2049 Orange Master 1
1700 - 1899 Violet Candidate master 1
1500 - 1699 Blue Expert 2
1350 - 1499 Green Specialist 2
1200 - 1349 Green Pupil 2
0 - 1199 Gray Newbie 2

In addition, the rating recalculating formula was slightly fixed to slow down the inflation. Now the sum of ratings will not be the constant, but is likely to be slightly falling. In fact, the changes are cosmetic and will be visible only on a series of contests.

I understand that for some of you it will be hard to say good bye to the favorite color, but let's look ahead with optimism — new victories will bring the lost color back color and help to win the proud title of a Grandmaster!


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By aropan, 6 years ago, translation, In English,

"Tryam" to everyone!

I am an authors of the today's contest. First of all I want to thank Artem Rakhov [RAD] (thanks to him, you'll understand my problems) and Maria Belova [Delinur] (those who know my English level will understand a huge of my thanks). Also thanks to everyone staff for the wonderful of the codeforces system. And also thanks to Sergei Tarasov [Seryi] and Andrey Tkachenko [TBGame] for ideas generating and testing.

Good luck and have fun.

Today, a breakdown of score will be slightly different from the standard - for the second division is 500-1000-2000-2000-2500 and 1000-1000-1500-2000-2500 for the first.

And one more, but certainly pleasant news - register ends exactly at the start of the round.

Analysis problem.

How it was.
At 19:35 Moscow time reported that in pretests for 123B - Squares have errors (a special thank to him). Indeed, a special case was not considered (a = 1, b! = 1 and symmetric to it). We have made decision to exclude tests covered by this case. There were a lot of such tests in pretests. Test generator has been fixed, and all tests were changed. After that all submits have been rejudged. As a result some submits with WA verdict could get the AC and vice versa.

What we have now.
We believe that the round should be rating. But if the situation with the problem 123B - Squares is strongly influenced to you, you can send an appeal with the evidence of this in the form of a personal message to RAD no later than 11pm on November 4. We can either do this round unrated for you or remove excess submits.
At the end of the system testing rating will be updated. If you have no appeals, it will be your final rating.

Sorry for the inconvenience.

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