By Akikaze, history, 7 days ago, In English,


(He last walked the Earth in round 538 btw.)

Hello Codeforces!

We are here to invite you to Codeforces Round #554 (Div. 2), which will take place at Apr/24/2019 17:35 (Moscow time).

The round will be rated for all Division 2 participants (with rating less than 2100), yet any Division 1 participants are welcome to join us out of competition.

The round will be cat themed. Raise your paws and prepare your catnips!

(Or even cat memes, while you're at it).

You will be given 6+1 problems ( 6 problems, one of them has 2 subtasks ) to solve in 2 hours. The round's problems were prepared by Xuan-Quang xuanquang1999 D. Nguyen, Duy-Bach Akikaze Le, Stefan stefdasca Dascalescu, Quang-Minh MofK D. Nguyen and our dear Codeforces coordinator Dmitry _kun_ Sayutin.

Gladly (or sadly), no interactive problem tonight!

Also, the tribute should be given to everyone within the team — we all make it possible:

  • Andrew GreenGrape Rayskiy for various problem suggestions and the infamous OMEGALULRIP influence. ;)
  • Xuan-Tung neko_nyaa Nguyen for testing the rounds and various suggestions in the core theme idea. Nya~.

Last but not least, I want to give a huge appreciation to MikeMirzayanov for the awesome Codeforces and Polygon platform, which makes this contest possible.

P/s: I will be at the Discord CP Community to discuss the problems after the coding phase. However, please follow the rules and don't discuss the problems during the contest by any means.

Wish everyone good luck and high rating!

P/s(2): Commies united!

P/s(3): A dear thank-you to Grigory gritukan Reznikov for the last-minute complete testing as well! ;)

UPD1a: Another comrade, Quang-Minh MofK D. Nguyen joined the fun! Kudos for the problem suggestion! ;)

UPD1b: The problemset contains 6+1 problems ( 6 problems, one of them has 2 subtasks ).

UPD2: Score distribution: 500-1000-1500-2000-2000-(2250+750).

UPD3: Editorial will be available tomorrow. Sorry for the waiting, we have quite a lot of things to polish. ;)

UPD4: The contest is finished. I hope that you're satisfied. And here come our winners ;)

Official participants:

  1. hamzzq
  2. davidHernandes
  3. oiyoayao
  4. It5t
  5. OnionGod
  6. IPL
  7. memset_inf
  8. dsgsjk
  9. FluffyT (the only official participants solved F1+F2, too bad he didn't solve E :<)
  10. _wxw_

Div.1 + Div.2 participants:

  1. dreamoon_love_AA (solved all problems!)
  2. pwild
  3. Heltion
  4. hamzzq
  5. natsugiri
  6. kmjp
  7. davidHernandes
  8. JeffreyHo
  9. betrue12
  10. KrK

UPD5: Editorial blog post is available.

Read more »

  • Vote: I like it  
  • +403
  • Vote: I do not like it  

By PikMike, history, 4 days ago, translation, In English,

Hello Codeforces!

On Apr/22/2019 17:35 (Moscow time) Educational Codeforces Round 63 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 problems and 2 hours to solve them.

The problems were invented and prepared by Roman Roms Glazov, Adilbek adedalic Dalabaev, Vladimir Vovuh Petrov, Ivan BledDest Androsov, Maksim Ne0n25 Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all participants!

Our friends at Harbour.Space also have a message for you:

Hi Codeforces!

This summer, we want to invite you to Tech Scouts, the two-week summer camp we run from the 8th-19th of July in one of Barcelona's leading international schools, St.Paul’s.

This camp, divided into Creative and Technical tracks, is designed to lay out the foundation of knowledge for high-school students in the fields of technology, mathematics, business and design. Both tracks are taught in English.

We would love to see you guys at our camp this year — if you’re interested in joining, or if you just want to know more, just head over to the Tech Scouts website.

This camp is for anyone passionate about tech or design, so if you know someone who might be interested, be sure to let them know too!

Ps. Don’t wait too long — you still have an early bird discount, but only until May 20th

UPD: The round will contain 6 problems.

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Um_nik 6 111
2 Cinro_9baka 6 207
3 Ilovebxy 6 247
4 ivan100sic 6 249
5 ainta 6 411

Congratulations to the best hackers:

Rank Competitor Hack Count
1 halyavin 292:-18
2 Haunted_Cpp 31
3 WileE.Coyote 30:-4
4 Disappointment 27:-1
5 czasem_tak_trzeba 23
790 successful hacks and 697 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A iaeyoayao 0:01
B MesyuraTheOldDumbGoblin 0:03
C NeKrasnyj 0:07
D FlyToTheSky 0:07
E Rezwan.Arefin01 0:17
F Um_nik 0:59

UPD: The editorial is out

Read more »

  • Vote: I like it  
  • +123
  • Vote: I do not like it  

By Lewin, 6 days ago, In English,

Hi Codeforces!

I'm excited to announce the Forethought Future Cup! It will consist of two rounds, an online round on April 20th, 11:05am PDT, and an onsite round on May 4th, 10:05am PDT. Both of these rounds will be rated and open for all participants. The top 25 local contestants near San Francisco will be invited to the Forethought office to take part onsite.

Each round will be a combined round. In the first round, there will be 8 problems in 2.5 hours. There will be at least one interactive problem in this round. Please read the interactive problem guide if you haven’t already.

The problems in this round were all written by me. Thanks to ismagilov.code, mohammedehab2002, Jeel_Vaishnav, Learner99, dojiboy9, fortune, y0105w49, KAN, arsijo for testing and coordination. Of course, thanks to MikeMirzayanov for Codeforces and Polygon, and for allowing us to host the round.


T-shirts will be awarded to all onsite participants. 25 shirts will also be randomly awarded to contestants in the elimination round with ranks 1 to 250. The onsite round will also have some monetary prizes:

  • First: $500
  • Second: $250
  • Third: $100
  • 4th — 10th: $50

About Forethought:

At Forethought, our mission is to use AI technology to augment human abilities and make everyone “a genius at their job”. Our main product is Agatha, an assistant that helps customer support agents answer cases more quickly and confidently by suggesting answers and triaging cases. We've raised over $10M in VC funding and were the winners of 2018 SF TechCrunch Disrupt Battlefield.

I joined Forethought back in December 2018. We are a small 12 person startup, and have a lot of competitive programmers on our team, including me, y0105w49, fortune, and dojiboy9 (our CEO, who is also an ICPC World Finals Judge). I’m happy to answer any questions about working here in the comments below or through PM.

We’re hiring! Please fill out this form if you are interested.


UPD 1 The scoring distribution will be 500-1000-1500-2250-2500-3250-3250-3750

UPD 2 Tutorial can be found here:

UPD 3 Congratulations to the top 5!

  1. tourist
  2. Benq
  3. Radewoosh
  4. yutaka1999
  5. ainta

Read more »

  • Vote: I like it  
  • +417
  • Vote: I do not like it  

By Dalgerok, history, 8 days ago, translation, In English,

Hi, Codeforces!

Codeforces Round #553 (Div. 2) will be held on Apr/18/2019 18:35 (Moscow time). Round will be rated for second division (rating below 2100). As usual, participants from the first division can participate in the contest out of competition.

My gratitude to arsijo and KAN for coordinating the round, Markellonchik (special thanks for the help in preparing one of the tasks), mohammedehab2002, Jeel_Vaishnav for testing, and also 300iq for the idea and preparation of one of the tasks, aleks5d and isaf27 for testing it, and of course MikeMirzayanov for Codeforces and Polygon systems.

In this round you will help the residents of the Kingdom of Kremland. I strongly recommend you to read the statements of ALL tasks (and of course, try to solve them).

Good luck!

UPD: Scoring distribution: 500-750-1250-1750-2250-2750.

UPD: Editorial

UPD: Thank you for your participation in this round! Congratulations to the winners!

Div. 2

  1. square1001
  2. hitonanode
  3. jaguar1996
  4. BoogieCy
  5. sansen

Read more »

  • Vote: I like it  
  • +257
  • Vote: I do not like it  

By Vovuh, history, 9 days ago, translation, In English,

This time I have nothing to say except that this round will consist of 7 different problems!


Hello! Codeforces Round #552 (Div. 3) will start at Apr/16/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

  • take part in at least two rated rounds (and solve at least one problem in each of them),
  • do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.


UPD: Thanks to le.mur for idea of one of the problems.

UPD2: Editorial is published now!


Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 ysluo2000 7 229
2 fake_delete_pls2 7 251
3 KefaKuma 6 178
4 Zhao-L 6 222
5 haimiaoyuzhao 6 240

Congratulations to the best hackers:

Rank Competitor Hack Count
1 wzw19991105 49:-4
2 ScreaMood 42:-1
3 I_love_Maria_Krylova 35:-5
4 Hacked_ 31:-1
5 Zombie358 30:-7
949 successful hacks and 502 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A MinatoYukina 0:01
B MinatoYukina 0:04
C Chess_fan 0:08
D nikizakr 0:07
E FluffyTT 0:21
F FluffyTT 0:09
G 1tst 0:14

Read more »

  • Vote: I like it  
  • +197
  • Vote: I do not like it  

By Aleph-0, 13 days ago, In English,

Hi Codeforces!

We are glad to invite you to our first Codeforces Round Codeforces Round #551 (Div. 2) which will be held on Apr/13/2019 17:05 (Moscow time). This round will be rated for participants with rating less than 2100. We will be glad to see participants from the first division to join out of competition as well!

In this round, as the best friend of Serval's, you are going to help him to solve the problems he meets.

The problems are prepared by bzh and me. We hope you will enjoy the round. :P

Great thanks to 300iq for coordination of this round, isaf27, gritukan, KAN, mohammedehab2002, learner99, aleks5d and Um_nik for testing our rounds, and MikeMirzayanov for the amazing Codeforces and Polygon platforms.

You will be given 6 problems to solve in 2 hours. Scoring distribution will be announced later.

Please pay attention that there will be an interactive problem in this round, so learn more about interactive problems here before the contest.

Good luck & Have fun! :D

UPD: Scoring distribution is: 500-1000-1500-1750-2250-2750.

UPD2: Thank you for your participation in this round! Congratulations to the winners!

Div. 2

  1. ihdignite
  2. NiroBC
  3. waaaaadreamer
  4. kidddddddddddddddddddddd
  5. xianhaoming
  6. __Ressed__
  7. nikolapesic2802
  8. xiaowuc1
  9. ei133333
  10. Kho0007

Div. 1 + Div. 2

  1. ihdignite
  2. kefaa2
  3. NiroBC
  4. uwi
  5. step_by_step
  6. waaaaadreamer
  7. mmmod_lqs
  8. teja349
  10. quailty

UPD3: Sorry for the delay. The editorial is available.

Read more »

  • Vote: I like it  
  • +490
  • Vote: I do not like it  

By 300iq, 3 weeks ago, translation, In English,


At Apr/06/2019 14:35 (Moscow time) we will host Codeforces Global Round 2.

It is the second round of a new series of Codeforces Global Rounds supported by XTX Markets. The rounds are open for everybody, the rating will be updated 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 2019:

  • 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.

The problems of this round were developed by a team of authors: 300iq, cyand1317, Aleks5d, RDDCCD, KAN, gen.

Thanks KAN for his help in the round's coordination, and also isaf27, lewin, osaaateiasavtnl., Errichto, arsijo, _kun_ for testing the round!


Congratulations the winners!

1) ecnerwala

2) tourist

3) Um_nik

4) Endagorion

5) Petr


Read more »

Announcement of Codeforces Global Round 2
Announcement of Codeforces Global Round 2
  • Vote: I like it  
  • +351
  • Vote: I do not like it  

By MikeMirzayanov, 3 weeks ago, In English,

ICPC World Finals 2019 will begin on April 4, 2019 at 11:00 (UTC). This event is the main event of the year in the world of sports programming!

In the past 20 years alone, ICPC participation has increased by more than 2000%. The contest evolved into its present form as a multi-tier competition in 1977, with the first finals held in conjunction with the ACM Computer Science Conference. Last year, ICPC Regional participation included 52,709 of the finest students and faculty in computing disciplines from 3,233 universities in 110 countries. We remind you that in the current world champion is the team of Moscow State University.

Codeforces wishes the teams to show a vivid and interesting contest. We wish to find beautiful solutions, write without bugs and enjoy many accepted problems!


ICPC World Finals 2019 English Broadcast:
Legends Live Stream (Endagorion + Petr + tourist):

Read more »

  • Vote: I like it  
  • +590
  • Vote: I do not like it  

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

Hey all!

We'll be running ICPC Connections this year at World Finals! ICPC Connections is powered by Lunchclub and is a way for contestants, coaches, and alums at World Finals to get to meet one another. We first ran Lunchclub at ICPC last year (thanks M.Mahdi for the shoutout!) and are excited to be back.

If you're in Porto this week and would be interested to meet fellow attendees, sign up at! And if you're curious to learn more about what we're working on, check out our main product here :)

Read more »

  • Vote: I like it  
  • +200
  • Vote: I do not like it