Hi!

I think everybody can remember a case when

Probably everyone remembers in practice a case when after implementation of correct algorithm you receive Wrong Answer. In such a situation, sometimes works: to send solution on another compiler.

Gerald and Nerevar have found severe bug, which gives one more argument to use the rule above.

Look closely, now it will be a miracle! 

Hello, Codeforces.

UPD: Round is finished. Thank you for your participation. Final results.

Today (16:00 UTC) we want you to take part in testing and unrated round with unussual scoring system. With your help we want to test new scoring, new type of problems and Codeforces system inside <iframe> tag.

Start time is 16:00 UTC

Go to the Contest!

There are two types of problems: logic puzzles and programming tasks.

A logic puzzle is a task that is designed to be solved by hand (but it is not forbidden to write some helper code to do this). Each logic puzzle consists of one or more tests. Each question can be answered separately from the others. There is a "Submit" button below each test. To answer the question, press "Submit" button. Your answer will be acknowledged and checked after the end of the contest. You can change your answer any number of times – only the last attempt is checked. For the correct answer to the question you will get the number of points which is indicated in the question description.

A programming task is want you can ussually see in Codeforces rounds. Solutions can be submitted at any time during the contest. A solution is evaluated on a fixed set of tests right after it is submitted. For each passed test, a contestant will get a fixed amount of points. The sum of points for all passed tests is the total points received by the solution. The contestant can submit a solution several times. The contestant will receive points for only one solution per problem. The solution with the maximum amount of points will be chosen.

The contest period is divided into two sections: Normal Time (NT) and Extra Time (ET). Each contestant is in only one of these at a time, but which one you're in can vary per contestant. In other words, when one contestant is in Normal Time, another one could be in Extra Time.

• Normal Time lasts for at most 30 minutes starting from when you click the button "Start Contest". (It could be less than 30 minutes if you start the contest less than 30 minutes before it ends). Points gained in Normal Time are the main way of deciding who wins. A participant with more points gained in Normal Time will always have a better ranking than a participant gaining fewer points in Normal Time.

• After Normal Time ends you can still solve problems until the contest ends. This period is called Extra Time, and points gained in Extra Time are the second way to order contestants. Thus points gained in Extra Time are used to rank participants that have the same number of points gained in Normal Time.

If a pair of contestants have the same number of points gained in Normal Time and the same number of points gained in Extra Time, they will be ordered according to the time (in seconds) of the last submission which gave them an improved positive score. For each programming task, we will consider only the best submission (or if there are many submissions which are equally correct, the earliest). For logic puzzles, if you submit new answers in Extra Time, whatever score you would have got is over-written by your new submission, and those points are changed into Extra Time points.

In other words, it's always safe to submit a new answer for programming tasks (you can only improve your situation). It is not always safe to do that for logic puzzles – consider carefully whether or not you want to do that.

The problems will be relativly easy but, I hope, they will be interesting, as will be the contest format.

We will be greatful for all community members who help us in testing.

With best regards, Ivan.

Unfortunately, the most anybody could solve was 7 problems out of 9 total. 1289 participants solved at least one problem — this is less than the last year's numbers, but not bad either. Anyways, the key point is the total quantity of fun the people had!

409A - The Great Game

The Most Intellectually Challenging Game In The World turned out to be the famous rock-paper-scissors. One could deduce this from the examples — ok, the rock () didn't look itself, but paper [] and especially scissors 8< looked really lifelike!

Team competition is organized like this: players are split into pairs, with one player of each team in each pair, and pairs play against each other (the first line of input has "moves" of first team's players, the second line — of second team's players). The team which scores more individual victories wins.

By the way, the game is not so trivial as it looks -

The contest is over; I hope you've enjoyed it :-) Editorial is here. See you next year!

The third April Fools Day Contest will take place on Tuesday April 1st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is. Thanks to kit1980, Skiminok, Gerald and MikeMirzayanov for their help in preparing problems.

In this round you'll be given several weird problems (the estimated quantity is between 6 and 10) and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces — well, unless the problem says otherwise :-)

Be warned, to enjoy competing in this round you'll need a sense of humor compatible with mine! Good luck, and have fun!

Hello everyone!

This Sunday, on March 30 at 11:00 MSK (March 30 at 07:00 UTC), Codeforces Round #239 for both divisions participants will take place. Note the unusual time of the round.

The problems have been prepared by me. I want to thank Codeforces team: tasks coordinator Gerald Agapov (Gerald) for invaluable contribution to the preparation of tasks and Maria Belova (Delinur), who has translated the problems. Also thank to Niyaz Nigmatullin (niyaznigmatul) for testing.

I wish you all good luck and have a good weekend!

UPD: You can see score distribution at the problems page.

UPD2: You can find editorial here.

Hello everyone!

Codeforces round #238 will start today at 19:30 in Moscow time. The round will be held in both divisions.

The round was prepared by me and cfk. This is the 4th round for me and the 2nd for Krisjanis. I think the problems this time are rather unusual and maybe even surprising. We have no doubt that everyone will find a problem that suits their taste! But you have to find it. (:

As always, thanks to Mikhail Mirzayanov (MikeMirzayanov) for Codeforces and Polygon systems, and Maria Belova (Delinur) for translating the statements. Big thanks to Gerald Agapov (Gerald) for helping in preparation of the contest. Me and Gerald had a chance to talk about the problems onsite during the Petrozavodsk winter camp, which I think was very productive.

We wish you a very exciting round!

UPD1: Score distribution:

DivI: 500 1000 2000 2000 2500

DivII: 500 1000 1500 2000 3000

The scoring for the problems is relative, so that the cost of each problem would be a multiple of 500 and closer to the objective estimate. Don't be afraid, the problems are not really that hard. (:

UPD2: Congratulations to the winners!

DivI:

1. al13n
2. Shef
3. scott_wu
4. sillycross
5. Komaki

DivII:

1. NelsonMondialu
2. L_Ecry
3. aaaaAaaaaAaaaaAaaaaA
4. xorfire
5. Hec

UPD3: Excellent round statistics from DmitriyH.

UPD4: The contest tutorial is published here.

Hi to all!)

Regular round Codeforces #237 for participants from 2 division will take place tomorrow March 19, 19:30 MSK. Traditional, participants from 1 division can take part out of the competition.

The problems were prepared by Igor Kudryashov (Igor_Kudryashov) and Gerald Agapov (Gerald). Also thanks to Michael Mirzayanov (MikeMirzayanov) for very cool system Codeforces and Mary Belova (Delinur) for translating the problems into english.

We wish everyone good luck, high rating and excellent mood)

UPD: Score distribution will be standard 500 — 1000 — 1500 — 2000 — 2500.

UPD 2: The contest is over, thanks to all participants.

Congratulations to the winners:

1. Pkqs09
2. juggler
3. zstu_bobo
4. kevinswat
5. Salvare004

UPD3: You can find the tutorial here

The CROC company and the Ministry of Defense of Russian Federation invite the schoolchildren of the 9-11th years of education in Moscow and the Moscow region to take part in a school programming championship. The championship is called Coder-Strike 2014. The championship will be held based on Codeforces.

Goals

We aim to support talented high school children, help to form the community of programming enthusiasts, develop future IT professionals. The modern industry offers scientific challenges that cannot be solved without profound knowledge in the field of algorithms and data structures. We want to provide out participants with potential ways of development of with the opportunities that open in front of high qualified professionals.

Participants

You can participate if you study at 9-11th school year of one of a high school of Moscow or Moscow region. You should also be over 14 years old at the moment of registration to the championship. In order to become a participant of the championship, you need to register before you take part in the qualifying round at http://crocok.ru/championship/. You should submit the participant application form to take part in the championship officially.

Schedule

The qualification round will consist of 2-3 easy programming problems, your solutions will be checked during the round. The rounds 1-2 and the finals will be conducted by the traditional Codeforces rules, you can learn more about them by these links:

• rules
• rules

Championship Finals

The championship finals will take place on April, 22 in the CROC company office on 5, Volochayevskaya street. The finalists will have an excursion along the company office an meet the leading specialists of CROC and the Ministry of Defence of Russian Federation. The time of the finals will be specified later.

The award ceremony will be on May, 20-23 on the exhibition by the Ministry of Defense called 'Complex Safety'.

Prizes

All the participants who make it to the finals get souvenirs from the CROC company and the Ministry of Defense of Russian Federation.

Participation Out-of-Competition

All the willing users can participate in the championship out of competition. In this case the application form is not required. The sorting rounds and the finals will be Codeforces rating rounds.

Soon (on March 16, 19:30 MSK) you are lucky to participate in Codeforces Round #236 for both divisions.

Problems have been prepared by me. It’s my first round for both divisions and I hope not last. I want to thank Gerald Agapov (Gerald) for help in preparation of this round, Ilya Los (IlyaLos) and Ignatyev Alexander (aiMR) for testing of problems, Mary Belova(Delinur) for translating the problems, Michael Mirzayanov (MikeMirzayanov) for marvelous Codeforces and Polygon systems.

UPD: Scoring system:

Div. 2: 500 — 1000 — 1500 — 2000 — 2500

Div. 1: 500 — 1000 — 1500 — 1500 — 2000

UPD:

Contest finished, congratulation for winners!

Div.2 :

1. vladb
2. iceiceice
3. LoneFox
4. ofpsxx
5. adsz

Div. 1:

• 1 sillycross
• 2 KADR
• 2 vepifanov
• 4 Endagorion
• 5 glassices
• 6 cgy4ever
• 7 rowdark
• 8 snuke
• 9 ftiasch
• 10 fsouza

UPD:

Editorial.

UPD:

Round Statistics from DmitriyH.

Hello everyone!

Codeforces Round #235 (Div. 2) will take place on March 10th at 19:30 MSK.

This is my first Codeforces round and I hope not the last one.

I'd like to thank Gerald Agapov (Gerald), Roman Rubanenko (Rubanenko), Sergey Oryshych (Oryshych) for helping me to prepare round, and Mariya Belova for translation of all problem statements into English.

Scoring: 500-1000-1500-2000-2500

GL & HF!

Top five:

1. UESTC_XHXJ

2. GoodByeAhu

3. OrzSKYDEC

4. simonlindholm

5. angelyue

Congratulations of participant hoanglmdiv2, who solved the problem E.

Unfortunately, my fault, in the round hit the problem that was previously used on another competition. Since it does not comply Codeforces, problem E will be deleted.

English tutorial