By PavelKunyavskiy, history, 3 hours ago, translation, In English

The International Olympiad in Informatics 2022 is scheduled to start in a month. To help you prepare today, we announce an online judge with IOI problems. Right here, on codeforces.

Available now

On you can find a contest for each day of each IOI contest since 2002. Participate virtually in a 5-hour contest or simply upsolve problems there! Virtual participants will appear in separate scoreboards for each year as well as in an upsolving scoreboard. Don’t forget to disable coach mode to appear in the upsolving scoreboard.

Future work

We have at least some problem materials for contests since 1998, but IOI has had competitive programming problems since 1994. Even if these problems are not very useful for training, they have significant historical value. Unfortunately, early-year materials on are incredibly bad, so if you have something (e.g., solutions, interactor, checkers, library sources), please contact me right away!

I am also considering adding original contest results as ghost participants to the scoreboards.

Let me know in the comments, what else would you like to see in the IOI archive?

How to help?

I'm sure some problems are misconfigured. The most probable errors are tests in wrong subtasks or changes in grader not mentioned in the problem statements. Let’s find them in upsolving mode, to avoid ruining the training process for contestants. If you have solutions (preferably partial solutions), please, become an early tester. Report issues via github repo. Pull requests to problem statements and validators are also always welcome there!

Please, contribute with contest materials for earlier IOI!

If you are a member of an IOI committee, help the project a lot by enforcing a better archival process for the future contests. In particular, it would be great to have as part of the public archive:

  • Statements in markdown
  • Any kind of non-English statements
  • Test data generators and tests generation command lines
  • Any description of solutions intended behavior or score
  • no new archive format every year :)

Also, you can donate to pavelkunyavskiy.crowdforces.near, to help pay for outsourcing some work, but that’s not necessary.

Special thanks

  • MikeMirzayanov and geranazavr555 for implementing a lot of stuff in Codeforces and Polygon
  • ligaydima , Dimitrys and especially Masha237 for help converting problem statements to polygon format.
  • lperovskaya for maintaining archive on, which become a great material source, as well as for proofreading this text
  • Petr for solutions and other materials of IOI2002 (and IOI2000, and IOI2001 I hope to publish later).
  • eduardische for showing me the old IOI site with problem materials, and Martins Opmanis for maintaining it.
  • yeputons for original archive resources and idea back in 2011

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By MikeMirzayanov, 30 hours ago, In English

Hello, Codeforces.

We have exciting news! Look at the logo. See the changes?

Yes, we are happy to announce our new sponsor and partner – the TON Foundation!

We appreciate their support!

The Open Network (TON) is a fully decentralized layer-1 blockchain designed by Telegram to onboard billions of users. The TON Foundation is aimed to further develop and advance the TON Blockchain and its related products for a mass audience.

Andrew Rogozov, founding member at the TON Foundation, says, "We strongly believe in the idea of competitive programming itself, because it is in the TON Blockchain DNA." The TON Blockchain protocol was designed by Nikolai Durov — who is a two-time ICPC world champion, a three-time IMO gold medalist, a multiple IOI medalist, and a co-founder of Telegram — and other winners of international competitions. Now the TON Blockchain core team consists of winners of blockchain contests held by Telegram.

The TON Foundation has already supported the CodeTON Round 1 earlier in March 2022. More than 22K users were registered, and 12K participants made at least one submission. "Codeforces is an unparalleled platform for developing the programming skills of coders all over the world. We are of one mind with the Codeforces team that such contests reveal a treasury full of talents," adds Andrew Rogozov.

I send rays of gratitude to Telegram and personally to Pavel Durov, who has supported our community for many years. With this help we have come a long way — we have run hundreds of rounds, developed the ecosystem, our community has grown hundreds of times. And we are moving forward! Support from the TON Foundation pleases with its succession.

I'm happy to announce that starting July 2022, we have the option to increase problem writer payouts. Hooray!

  • Div. 2: $300;
  • Div.1 + Div. 2: $600;
  • sponsored round: $900.

In addition, we continue to encourage payments in cryptocurrency. In this case, we pay out +25%. I look forward to new rounds on our platform.

— Mike Mirzayanov

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By cadmiumky, history, 3 weeks ago, In English

Hello, Codeforces! Or, as we like to say in Romania: Noi nu spunem asa ceva, Codeforces!

We are proud to finally invite you to participate in Codeforces Round #804, which will start on Monday, July 4th, 2022, 14:35 UTC You will be given 5 problems and 2 hours to solve them. We greatly recommend to read all the problems, statements are very short and straight to the point.

In this round, the theme is not Independance Day related. I know, maybe we should've made the theme "Freedom", but we are not Americans and the puns within the problems were already written.

Joining me on the problem setting panel are:

Also, we would like to thank:

  • intrusiv for not deserving to be publicly named
  • tibinyte for being a "codechef carry".
  • Gheal for getting order #804 at KFC.
  • lucaperju and VELJAODI for inviting some of the testers :)
  • Artyom123 for captivating coordination, rejecting only Boring tasks. 9 div2Bs to be precise
  • antontrygubO_o for improving one of the tasks!
  • NEAR for supporting this round, details can be found in this post.
  • MikeMirzayanov for great platforms, Codeforces and Polygon!

Here is the scoring distribution: $$$500 - 1000 - 1500 - 1750 - 2500$$$.

Good luck & have fun & the third part!

UPD1: Editorial is up!

UPD2: Winners!

Div 2:

Div 1:

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By Harbour.Space, history, 3 days ago, In English


Hey, Codeforces!

Harbour.Space University and Leagues of Code make a programming camp in Barcelona!

Leagues of Code is the official trainer of the Spanish National Olympics Team in Informatics.

Our Summer Camp is a training program that will teach participants competitive programming. It will take place in Barcelona and online on July 18-29, both participation formats are available. We are inviting students ages 10 to 24, interested in improving their skills or seeking for intensive, high level training prior to the IOI. Teachers in the camp will be mhq, MaksymOboznyi, pashka, and others. Participants will be divided into classes based on their level and previous experience. Classes will be held in English.

Join a coding camp that brings you the brightest stars in tech!

Get 30% discount for an on-site participation or 50% discount for online participation with promocode CFLOC2022.

Learn more →


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By flamestorm, 10 days ago, In English

Hi Codeforces!

ScarletS and I are glad to invite you to Codeforces Round #803 (Div. 2) which will be held on Jun/28/2022 17:35 (Moscow time). The round will be rated for participants with rating lower than 2100. The theme of the round will be déjà vu! (Wait, wasn't that already a theme before?)

Thanks to the people who made this round possible:

Thanks to NEAR for supporting this round, details can be found in this post.

You will have 135 minutes to work on (and solve!) 7 problems. At most one of the problems will be interactive. Make sure to read this blog and familiarize yourself with these types of problems before the round!

The scoring distribution is $$$250-500-1000-1500-2000-2500-3250$$$.

Good luck, and see you on the scoreboard!

UPD: Editorial is out!

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By feecIe6418, 2 weeks ago, In English

Hello Codeforces!

On Jun/25/2022 17:35 (Moscow time) we will hold Codeforces Global Round 21.

It is the third round of a 2022 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

  • 30 best participants get a t-shirt.
  • 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2022:

  • In each round top-100 participants get points according to the table.
  • The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
  • The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2022 supported the global rounds initiative!

All problems except one are authored and prepared by me. The other problem is authored by gyh20.

We would also like to thank the following people:

Round information:

  • duration: 2 hours and 15 minutes
  • number of problems: 8
  • score distribution: 500-1000-1500-2000-2000-2500-3250-4000

We are looking forward to your participation!

Upd Editorial

Upd Winners!

  1. ksun48
  2. jiangly
  3. Um_nik
  4. Petr
  5. maroonrk

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Announcement of Codeforces Global Round 21
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By ch_egor, 3 weeks ago, translation, In English


This Sunday will take place All-Russian olympiad for students of 5-8 grades, in the name of Keldysh. Good luck to all the participants! Olympiad is conducted under the guidance of the Moscow Olympiad Scientific Committee, in particular GlebsHP, ch_egor, Endagorion, vintage_Vlad_Makeev, Zlobober, meshanya, cdkrot, voidmax, grphil, fedoseev.timofey and, of course, Helen Andreeva.

We are happy to announce the Codeforces Round #802 based on the problems of this olympiad! It will be a Div. 2 round, which will take place at Jun/19/2022 12:05 (Moscow time). You might have already participated in rounds based on the school olympiads, prepared by Moscow Olympiad Scientific Committee (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704, 707, 727, 751, 775). Please notice the unusual time.

The problems of this olympiad were prepared by Siberian, _overrated_, Igorbunov, Ziware, _tryhard, EntitledMonkey under the supervision of fedoseev.timofey.

Thanks to 74TrAkToR for their help in organizing the Codeforces version of this contest and one of the problems, MikeMirzayanov for the Codeforces and Polygon.

Also I would like to thank the Tinkoff company and personally Tatyana TKolinkova Kolinkova for great help with organizing the competition.

Thanks to NEAR for supporting this round, details can be found in this post.

Good luck!

UPD1: Thanks to Um_nik, mhq, MichsSS, kucipendik, TeaTime, devid, Mangooste for testing.

UPD2: Scoring distribution: 500 — 1000 — 1500 — 1750 — 2500 — 3000

UPD3: Winners!

Div. 2:

  1. teacherone
  2. zsxdcfv
  3. AndrescuIII
  4. rhzmydd
  5. Yuki991

Div. 1 + Div. 2:

  1. SSRS_
  2. noimi
  3. Fysty
  4. peti1234
  5. teacherone

UPD4: Editorial

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By jdurie, 3 weeks ago, In English


Hi, Codeforces!

We welcome everyone to take part in Codeforces Round #801 (Div. 2) and EPIC Institute of Technology Round, which will start on Jun/18/2022 17:35 (Moscow time).

The round will be rated for participants of Division 2 with a rating lower than 2100. Division 1 participants can participate unofficially in the round.

You will be given 5 problems and 2 hours to solve them. One problem will consist of multiple subtasks.

The score distribution will be 500 — 750 — 1250 — (1250+1000) — 3000.

The round was prepared by me, ki0apa, and akifpatel.

We would like to say a word of appreciation:

Good luck to all the participants!

Update: Editorial is out!

About EPIC Institute of Technology

Recently, in our blog, we have introduced the educational project of EPAM called EPIC Institute of Technology.

EPIC Institute of Technology, a part of EPIC — EPAM Product Innovation Center, is truly a unique educational project driven by the Deltix team under the EPAM Systems umbrella.


EPIC Institute of Technology is an accelerator for the best talents. Our students will acquire hands-on experience in one of the selected major programs, all of them are highly demanded right now on the top projects, together with the fundamental knowledge, so indispensable for real professionals. Successful graduates will have a unique chance to jump start their career on the most challenging and interesting EPAM projects worldwide. You will join the community of intelligent and driven individuals and have an honor to work with and learn from them.

Here are the answers to the most common questions:

How much does education cost?

EPIC Institute of Technology is completely free. There are no fees to register for exams or tuition fees.

How is the educational process organized?

Each program lasts exactly one year. The academic year consists of two semesters. Courses in the first semester are the same for all programs. Courses in the second semester depend on the selected major program.

Students will take an intermediate assessment in the middle of the semester. The final grade will be given for each course at the end of each semester. The grade a student gets for each training course, depends on the quality of the laboratory work and participation in lectures and practical classes.

Lectures, practical classes, seminars, conferences, and other interesting activities are provided for students on all training courses.

How will the classes be held?

All classes will be held online. Lectures and practical classes will be held at the specified time according to the provided schedule. Recordings of all classes will be available for those students who, for any reason, were not able to attend.

In what language will I study?

All programs are in English language.

What will happen after graduation?

EPIC Institute of Technology graduates will get a diploma and an offer to join, either as an intern or a full-time position, one of the hot EPAM projects where skills acquired at EPIC Institute of Technology will be demanded.

Please visit our website to learn more about EPIC Institute of Technology and the available programs. If you have any questions, you can quickly ask them in our chat.

Join us →

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By AmShZ, 3 weeks ago, In English

Hi Codeforces!

Keshi, alireza_kaviani and I are delighted to invite you to participate in Codeforces Round #800 (Div. 1) and Codeforces Round #800 (Div. 2).

  • Start time: Jun/16/2022 17:35 (Moscow time)
  • Duration: $$$120$$$ minutes
  • Number of Tasks: $$$6$$$ for both divisions
  • Rated range: ($$$-\infty$$$,$$$1899$$$] for Div2, [$$$1900$$$, $$$\infty$$$) for Div1

We are honored to have set the 800th Codeforces round. We wish this wonderful platform all the best along with many other exciting rounds.

Huge thanks to the following people:

Thanks to NEAR for supporting this round, details can be found in this post.

We have worked hard to keep the statements clean and the pretests strong!

Please read all of the problems and their notes, enjoy your time and solve as many as you can! Good luck have fun to everyone!

The scoring distributions will be announced later.

UPD: Here are the scoring distributions:

  • Div. 1: 750 1000 1500 2250 2500 3000

  • Div. 2: 500 1000 1500 1750 2250 3000

UPD: Editorial is out!

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By MikeMirzayanov, 3 weeks ago, In English


I always like to think that Codeforces is not only a place where you come to compete but also a place where you can learn. Learn new things.

Two years ago, we launched the EDU subproject, a platform for publishing classes. There are already several classes, but there are so many interesting topics around!

The Codeforces team can write the platform, make the technical foundation, but it would be great to write content with the support of the community.

Thanks to the support of competitive programming alumni, we have a budget for targeted grants for the preparation of new classes in the EDU section. Hope we have new content soon!

We are looking for lesson authors who could prepare and record one or more lessons. Those who are now red or have ever been red are invited.

We assume that one lesson (class) consists of:

  • 3-5 steps: break the lesson into logical parts,
  • video materials explaining the topic (usually, the total duration is 60-120 minutes),
  • text summary
  • a thematic training set of problems with a wide range of complexity (from the most basic on this topic to quite tricky ones)
  • first of all, we would like to cover the main topics of competitive programming — DP, graphs, basic data structures, etc.

Please note that we expect you to record and edit the video by yourself. Look at already recorded lessons to understand the expected format and structure of lessons. We have a rich history of teaching, so you can count on our advice and assistance in preparing lecture plans and problems. If video editing scares you, then here we can help.

We invite you to help grow the community and make history. I am sure that the recorded classes will be watched by tens of thousands of people (or more?).

The reward for recording one class is $1000.

If you are now red or have ever been red and you are interested in this offer, then fill out the form (open until June 28th).

Apply →

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