By Kniaz, 4 days ago, translation, In English,

Hello everybody!

I am glad to announce that at 19 January 2017 18:05 MSK will take place Codeforces Round #392 for participants of Div.2. Participants from the Div.1 may participate out of the competition as usual.

You will be offered 6 problems and 2 hours for solving them.

Great thanks to Nikolay Kalinin (KAN) and Alexey Vistyazh (netman) for their help with the contest preparation, Tatiana Semenova (Tatiana_S) for translating the statements and Mike Mirzayanov (MikeMirzayanov) for the Codeforces and Polygon systems and also for help with ideas of some problems and their preparation.

It's my second round and I hope that you like it more than the previous one. Fair rating to everyone!

UPD: Scoring 500 — 1000 — 1500 — 1750 — 2500 — 3000.

UPD: Editorial!!! I want to thank Mikhail Piklyaev (PikMike) and Tatiana Semenova (Tatiana_S) for translation of tutorial!

Congrats to the winners!

Div. 2

I wolf29

II alexwice

III WhyamIhere

4 TaTaPiH

5 Life_chicken

6 RewriteHarvestFesta

7 D0zingBear

8 whzzt

9 _Lucas97

10 Clayton

Div. 1

I W4yneb0t

II sd0061

III irkstepanov

4 wolf29

5 I_love_Tanya_Romanova

6 HellKitsune

7 kraskevich

8 kmjp

Read more »

  • Vote: I like it  
  • +273
  • Vote: I do not like it  

By Miyukine, 9 days ago, In English,

Hello everyone! The first round of the 8VC Venture Cup 2017 will be held on Sunday.

I am honoured to be the problemsetter of the round. Reyna helped me a lot. Huge applause to KAN for his valuable coordinator's help, and MikeMirzayanov for his admirable work for the Codeforces comunity. I also want to thank testers very much (Alexey ashmelev Shmelev and Alex AlexFetisov Fetisov).

This round is a first stage of 8VC Venture Cup 2017. If you want to acknowledge yourselves with the competition, try here.

The main character of the round is PolandBall. It's a small friendly Ball who lives in a forest along with other Balls. You'll surely like it :)

I tried to fulfill your demands with a various, interesting and challenging problems described in a concise way.

Hope to see you soon, good luck and have fun!

UPD1: Scoring 500100015002250250027503500.

UPD2 Thank you for participation! Contest is over. Did you like the problemset? Feel free to comment =)

UPD3 Editorial

UPD4: Winners

  1. tourist
  2. moejy0viiiiiv
  3. W4yneb0t
  4. ilyakor
  5. ainta.

Hope you've had a good time with PolandBall solving the problems.

Congratulations to all the winners and TOP-200 who advances into 8VC Finals =)

Read more »

  • Vote: I like it  
  • +397
  • Vote: I do not like it  

By MikeMirzayanov, history, 3 weeks ago, In English,

Hello Codeforces!

I'm pleased to announce the first championship hosted on the Codeforces platform. Welcome 8VC Venture Cup 2017!

8VC will be hosting a coding championship on Codeforces. The championship will begin on January 15 and take place in 2 rounds.

The contest will occur in two rounds:

  • The Elimination Round is online and takes place on January 15, 17:05 (UTC). Elimination Round follows regular Codeforces rules and consists of 7-8 problems. For this round, the complexity of the problems will be comparable to a regular Codeforces round. There are no eligibility restrictions to participate in the round.
  • The Final Round takes place on January 22, consists of 5-6 problems, and uses regular Codeforces rules. The complexity of the problems is higher than a regular Codeforces round. We will invite the top local finishers in Elimination Round to Woodside, CA to compete in the Final Round. In addition, we will invite the top 200 overall finishers to compete online.

Cool prizes are offered to winners and best participants.

  • Overall 1st place — $2000
  • Overall 2nd place — $1000
  • Overall 3rd-5th places — $500 each
  • Overall 1-50th place — t-shirts with 8VC and company logos
  • Local Winner — Dinner with Joe Lonsdale (founder of Palantir, Addepar and 8VC) and other Silicon Valley technologists
  • Local top finishers — Opportunity to meet with leadership from 8VC portfolio companies

8VC, which consists of Joe Lonsdale (co-founder of Palantir) and his core team from Formation | 8, is a Silicon Valley venture capital firm that invests in industry-transforming technology companies. The team's investment portfolio includes companies such as the selected companies below, and a host of other top technology platforms that leverage modern algorithms and data science to power their core business processes.

Connect to 8VC

Read more »

  • Vote: I like it  
  • +154
  • Vote: I do not like it  

By tanujkhattar, history, 12 days ago, In English,

Hello Everyone!

I would like to invite you to CodeCraft-17, which will take place on Thursday 12th January 2017, 9:05PM IST. The round will be a Div1 + Div2 combined round and is rated.

Felicity, IIIT Hyderabad presents Threads ‘17, the magnificent annual technical fest, is finally here in its 13th edition! With a plethora of intellectually engaging online contests in various fields of programming, mathematics and general knowledge, Threads is a celebration of the spirit of computing and engineering. The grand algorithmic sprint called CodeCraft, parallel programming in Kernel Cruise, mathematical enigmas in Gordian Knot, jeopardy style CTF event called Break In, overall Threads '17 has something to offer for every kind of computing enthusiast!

Codecraft Poster

I would like to thank Nikolay Kalinin (KAN) for helping us in preparing the contest,to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon platform and the Threads Team for helping in preparation of the problemset.


  • Top 25 participants win Codeforces T-shirts.
  • Additionally, 25 randomly chosen participants from top-500 will also win a Codeforces T-shirt.

You will be given seven problems and three hours to solve them. The scoring distribution will be announced later. Good luck everyone!

UPD: The constraint of registration for eligibility to prizes has been removed. Everyone who participates in the round is eligible for prizes. Sorry for the inconvenience caused!

UPD2: Scoring is 500 — 1000 — 1500 — 2000 — 2500 — 2750 — 3500

The contest has ended. Thank you all for participating. Hope you liked the problems.
It was our first codeforces round and it was really exciting for us to see how the contest progressed!
Editorials and list of T-shirt winners will be published soon.

Congratulations to the winners!

  1. tourist
  2. W4yneb0t
  3. anta
  4. Um_nik
  5. ershov.stanislav
  6. LHiC
  7. jcccccccccccccccccccccsb
  8. GlebsHP
  9. jiry_2
  10. Egor

UPD4: Editorial has been posted.

UPD5: The random t-shirts winners will be announced tomorrow according to the algorithm described in this comment.

Read more »

  • Vote: I like it  
  • +532
  • Vote: I do not like it  

By netman, history, 2 weeks ago, translation, In English,

THi Codeforces!

I'm glad to announce that today at 17:35 MSK will take place first round in the new year — Codeforces Round #390 for the second division. Traditionally, first division participants will be able to take part out of competition.

Round was prepared by me, Alex netman Vistyazh.

Many thanks to Nikolay KAN Kalinin for his help in contest preparation and Mike MikeMirzayanov Mirzayanov for the Codeforces and Polygon platforms.

You will be offered five problems and two hours to solve them.

Scoring will be announced closer to beginning of the round.

UPD: Scoring is 500 — 1000 — 1500 — 2000 — 2500


There were some troubles during contest — in problem C first pretest wasn't equal to first sample, and unfortunately this problem was solved much worse than we expected. I made conclusions and next time I will estimate difficulties of problems more responsibly.

Congratulations to the winners!

Div 2:

  1. YJZC
  2. markysha
  3. Yamada
  4. LLI_E_P_JI_O_K
  5. I_love_livlivi
  6. wolf29
  7. Nunnally
  8. AkaneSasu
  9. GemaSamuca
  10. EliteWantsYou

Div 1:

  1. kraskevich
  2. gritukan
  3. uwi
  4. halyavin
  5. sugim48


Editorial posted!

Read more »

  • Vote: I like it  
  • +252
  • Vote: I do not like it  

By xiaodao, history, 2 weeks ago, In English,

Hello, everybody!

Some of clever you maybe already noticed, 2016-2017 ACM-ICPC China Finals were already available in gym several days ago, and I'm glad to share another contest with you on this weekends.

China Collegiate Programming Contest is a local algorithm contest held since last year. This year, it has 3 regional as well as 1 finals. The finals have been hold 2 weeks ago before the ACM-ICPC China Finals, many of us regarded it as a rare practice chance before the latter one.

I think most of you on Codeforces haven't seen the problems yet, so this time, I'd like to schedule a virtual contest with you guys on 2017, Jan. 7th, 12:30:00 (MSK).

Thanks for mathlover who help me import the scoreboard!

Good luck and have fun!

Read more »

  • Vote: I like it  
  • +164
  • Vote: I do not like it  

By MikeMirzayanov, 2 weeks ago, translation, In English,

Hello, Codeforces!

New year brings changes to the Codeforces team. As you probably know GlebsHP completed his work as the chief coordinator of Codeforces. Gleb, thanks a lot! You did an excellent job and coordinated a lot of interesting rounds. You're a professional, an interesting person, you have impeccable taste to problems, and you proved to be brilliant and talented writer. Thank you that you were with us! Hope to see your tasks on Codeforces many times again!

Nikolay KAN Kalinin came to Gleb's place. He is also an experienced participant, Nikolay has already held several rounds as a coordinator. KAN seriously engaged in programming contests since he was 12 years old. His major achievements: he won twice All-Russian School Team Olympiad; he won All-Russian School Olympiad (the 1st place!); he has two Gold medals in International Olympiad in Informatics (IOI 2013, 2014), bronze medal in the ACM-ICPC World Finals 2016 and he took the third place at the RCC 2016. This is the highest level! I am very pleased that Nikolay has joined the Codeforces team. I am confident we will succeed!

And here there is the first innovation of 2017 year. The idea to ​​organize work with proposals has swirled in my head for a long time. It turned out well: KAN visited Saratov to get acquainted with the whole Codeforces team and celebrate the New Year together. And we not only had a good time, but found some time to discuss details how we see our work with writers. Here's what happened.

Writers Requirements

All the functionality described below is only available for experienced contestants and writers of past rounds. There are requirements on the number of rated contests depending on your color (magic does not work here, sorry).

color the minimum number of rating contests
blue 25
violet 15
orange 5
red no restrictions
Was already a writer in the past no restrictions

Please do not assume that the requirements are too strict. Our experience shows that it is hard to work with writers who are inexperienced as contestants . If you are a writer/jury member with experience in other competitions/events, please write KAN a private message about your wish to prepare a contest and describe your experience in this area. Be respectful to the coordinator decision, if it prompts you to achieve the general formal requirements prior to review your proposal.

Writers Reward

Preparation of the round is fascinating, but large and demanding work. We have the opportunity to reimburse the effort of the writers according to the following tariff:

Round Type $
Div 1 + Div 2 $250 + $50*
Div 2 $100 + $50*

An asterisk denotes a bonus, which is issued in case of work in time, without any issues

If a round is a part of a championship, there is an additional bonus, which is discussed separately.

I dream to raise reward to writers. I dream to see the most experienced, the most creative and interesting writers give our users the opportunity to participate in their rounds on Codeforces! Codeforces rounds attract record number of participants from around the world (the next frontier is 10000 registrations!), I personally offered a large number of problems — the chance to give an interest to participants is priceless.

Please send us your problems, spend contest proposals! We can make a platform, we can build a process, we can host championships. But we can't invent and prepare problems on each round.

How to propose a contest (можно читать всё!)

Those who meet the requirements will find the special link “propose a contest/problems” in the personal menu in the right sidebar. Click on it and you will have the opportunity to offer a contest, add problems to it. Read all instructions carefully. Carefully prepare and submit your proposal for a contest and for problems. I think that user interface is simple and intuitive.

Now, you can use only new system to submit proposals. If you have already received an answer from KAN for current proposal, you shouldn't transfer it to the new system. If the response has not been received yet and the proposal in actual, please, use the new system to send the proposal again.

The discussion of your ideas will be in comments mostly. Perhaps at a later stage it will be a possibility to communicate with the coordinator through any messenger.

Please be active, respond to coordinators' questions in time, make the proposed changes quickly. Remember that Codeforces coordinators are very experienced as participants and as reviewers . Their opinion is important, always balanced, and they have the highest priority in any decisions on the problems.

When the work goes to the preparation of problems in Polygon, the pre-read the examples of well-prepared problems, read all articles about using testlib. It is not difficult, but once you understand, you will be able to prepare high-quality problems for any Olympiad!


Later we come up with how to adapt the system for educational rounds (they come back!), for educational problems. With the new system we will get rid of lost proposals and can significantly automate and organize the process of working with them. I am sure that the system will be upgraded in the future and will become more flexible, more comfortable, more functional.

I hope that in 2017 we will host a lot of interesting rounds with your help. I hope you are waiting for them as well as I'm waiting!


Read more »

  • Vote: I like it  
  • +710
  • Vote: I do not like it  

By MikeMirzayanov, 3 weeks ago, translation, In English,

Somehow it turns out that for me, each coming the New Year means more and more. This is an excellent opportunity to take stock, to breathe fresh air and to go through a kind of catharsis. This is a rare opportunity to be with the family, dress up in Santa Claus and just have fun.

Holidays give me a clear criterion that I do the right things. If during the holidays, I begin to think about it, to recall some deferred ideas, eager to implement something new. So I’m doing right things. My things. And now exactly the same as in several recent years: during New Year holidays I write code for Codeforces, trying new technology or simply I’m making minor changes in testlib. It is necessary to me: at this moment are no deadlines, do not press the obligation. Just now, at 3 am, I can not break away from being able to do something new. I would like to take a moment and realize that spun in my head the whole year.

I'm insanely happy to huge number (9144!) of registrations on Good Bye 2016. Your desire to grow, to learn new things, solve problems and invent, improve skills and compete, all this things give me strength and desire to develop the platform.

I wish you not to lose the fire in eyes, when you meet an interesting problem. I wish to continue to find pleasure in each contest or round. I wish to find, to solve more and more complicated and interesting problems. Victories and achievements! Wish you to solve all things which you didn’t solve in 2016!

Happy New Year!

But you, please read this post entirely. It is important to me. It draws the symbolic line to me and the whole Codeforces team. And, of course, below it is written about change handles gift and a colorful masquerade of ranks. Go!

Read more »

  • Vote: I like it  
  • +1405
  • Vote: I do not like it  

By GlebsHP, history, 3 weeks ago, translation, In English,

Dear community!

It was a fantastic year, with great pleasure I took a role of Codeforces Coordinator. This year I learned a lot, communicated with wonderful people and realized how valuable this work is for thousands of people. I would like to thank you all for these great moments! I strongly believe that there are many cool rounds and interesting problems ahead as I'm passing this duty to Nikolay KAN Kalinin!

Please, watch my New Year's speech (Russian language, English subtitles):

P.S. Special thanks go to Maxim zlobober Akhmedov and Oleg shhdup Mingalev who helped me prepare this video.

Read more »

  • Vote: I like it  
  • +1069
  • Vote: I do not like it