Hello Codeforces!

On Apr/12/2021 17:35 (Moscow time) Educational Codeforces Round 107 (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 or 7 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 Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

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

Calling on all Codeforces,

Harbour.Space University is offering a unique opportunity to study in Barcelona for those who are interested in joining our young and dynamic competitive programming team. We accept medalists and top performers of IOI, IMO, ICPC, and participants with Codeforces rank above 2000.

Harbour.Space has a single, key requirement: be passionate and motivated to learn and/or work in the field of competitive programming in the long term. Even if you have already exhausted all your ICPC attempts, you are still welcome.

Join us to help build a comprehensive system of preparation for IOI and ICPC for the next generations! We believe that if you have the talent and determination to succeed, you can. We want to help you make it happen.

In addition to courses taught by some of the world's foremost experts in their fields, Harbour.Space offers these benefits upon acceptance for this scholarship:

• A full tuition fee waiver (Bachelor and Master degrees)
• Student visa
• Private health insurance
• Monthly living allowance*

In return, we demand dedication to learning and improving yourselves:

— Study three hours per day
— Train continuously for ICPC, if you are still eligible for participation
— Intern four hours per day

Ready to formally submit your application? Please register on our website, attach your latest CV, and pay a non-refundable €125 application fee. The fee guarantees we can process every single application in a fair and timely manner, and maintain the highest possible standards of assessment.

Our admission process is a holistic review of each candidate's abilities, achievements, and potential to create something exceptional.

You may choose to study in the following areas of specialization:

1. Computer Science
2. Data Science
3. Cyber Security
4. Front-End Development

All our degrees are taught in English. If you want to learn more about our programs please visit our website or contact our admissions office.

*The exact living allowance level throughout the entire duration of studies depends on the performance during the interview and on the overall performance. As a guidance, it is in the range of 500-1500 EUR.

Harbour.Space University Team

Congratulations to the winners:

145 successful hacks and 1221 unsuccessful hacks were made in total!

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

UPD: Editorial is out

The Programming Club, IIT Indore is proud to present our flagship event, Divide By Zero! The contest will take place on Apr/11/2021 17:35 (Moscow time). This round will be rated for all participants with a rating lower than 2100.

Thanks to the following people for making the round possible:

• KAN for coordinating throughout the round.
• kalpitk, ajit and 7dan for setting the problems.
• dvshah, bhanushali, sundesh, AniketSangwan, krishanu21saini, somyamehta_24 and hk2102 for their contribution to the problemset.
• Um_nik, dorijanlendvaj, chctxdy68, Osama_Alkhodairy, ScarletS, Discombobulated, kassutta and Jellyman102 for testing the problems.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms.

There are 6 problems, and 2 hours to solve them. The points distribution will be updated later.

Update: The scoring distribution is 500 -- 1250 -- 1500 -- 2000 -- 2750 -- 3000.

Update: Editorial is up.

Update: Will update this blog with winners within 2 days, so stay tuned.

PRIZES: Twenty Codeforces T-shirt will be given to:

• Top 10 Indian Participants
• Random 10 from top 100 (rank 11-100) Indian participants

Hope you guys enjoy the contest! See you on the leaderboard!

Hello, Codeforces!

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Hello! Codeforces Round #713 (Div. 3) will start at Apr/10/2021 17:35 (Moscow time). You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended 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 7 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 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.

The problems for this round were invented by MikeMirzayanov, Supermagzzz, Stepavly and sodafago.

Thanks Gassa, darkkcyan, bfs.07, Tzak, songsinger, Mukundan314, iankury, drunya, sodafago, ChOmPs, Programmer, Khairy, IITianUG, Rox for helping with testing the round!

Thanks to MikeMirzayanov for platforms and coordination of our work. Good luck!

</almost-copy-pasted-part>

Editorial: https://codeforces.com/blog/entry/89535

Hi Codeforces!

Yes, I know it's already April. Time flies so fast lately! Exactly a year ago we were just learning all the "delights" of lockdown.

So let's remember this 2020! What was it like? I don't know about you, but we had a hell of a lot of work.

I will now show you some graphs and you will be very surprised. Lockdown effect? Of course, but we did our best too.

Many thanks to everyone who did not stand aside! In 2020, we celebrated our 10th anniversary and crowdfunding money helps us grow and move forward. You helped us and each other. Thank you. Thank you for your contribution!

We've been working hard all year to make this community a better place. Did it work out? It's up to you to judge. Many thanks to everyone who invested time and effort:

• geranazavr555, kuviman, cannor147 helped a lot with development and new features;
• Una_Shem provided great organizational assistance;
• our problem coordinators are the greatest: KAN, antontrygubO_o, isaf27, 300iq, significant assistance was provided by BledDest, adedalic and Nebuchadnezzar, vovuh for preparing Div3 rounds;
• stingray advised and helped set up the network;
• our friends from VK for their help in our infrastructure;
• and help of problem writers and testers is immortal!

Time to take stock of 2020.

Partner Events

We are pleased to hold programming competitions with companies or for companies. I'm sure this is a great way to support the community of young programmers and hire talented candidates. Here is a list of our main partners this year:

• Telegram and personally Pavel Durov is supporting Codeforces activities for many years, every regular round is held with their help, thank you!
• ICPC — in 2020 we held several joint events (and we liked it!), I hope there will be more
• Mail.Ru — Technocup and Russian AI Cup
• VK, VK Cup — now a personal multi-track competition for Russian-speaking programmers
• XTX Markets, Codeforces Global Rounds — a series of 6 rounds with a separate scoring and souvenirs for the best participants
• Harbour.Space University — a series of educational rounds, the selection of summer school Tech Scouts
• JetBrains, Kotlin Heroes Rounds — Kotlin programming language contests
• Huawei — research competitions (marathons) with elements of machine learning
• Raiffeisenbank — round for both divisions with cool prizes
• Grakn Labs — round for both divisions with money prizes
• Microsoft, Microsoft Q # Coding Contest — unusual quantum computing competition

Hello everyone!

After all online qualifiers, we are pleased to announce that the Northern Eurasia Finals and ICPC 2021 semi-final offline stage will take place this weekend on April 3-4!

ICPCLive broadcast Standings

Mirror Problems Problems solutions

In December 2020, we announced that 50 student teams out of 330 were selected for the Northern Eurasia Finals. Most of the teams will compete in St. Petersburg. Still, some teams will compete at Minsk, Tbilisi, and Riga sites due to travel restrictions between countries.

NERCNews is going to monitor the championship and report on the main events! We will post links to the results table, contest tasks, contest mirror, and analytics published on the official website.

UPD today were qualified for ICPC 2021 World Finals next 12 teams:

• SPb ITMO: Insert your name (Budin, Korobkov, Naumov)
• HSE: Overtrained (Gorokhovskii, Safonov, Rakhmatullin)
• Moscow SU: Nonames (Koshelev, Chunaev, Kalendarov)
• St. Petersburg SU: LOUD Enough (Bochkov, Makarov, Gaevoi)
• Saratov SU: N (Petrov, Piklyaev, Meshcheryakov)
• SPb HSE 1: Lemon Tree (Makhnev, Surkov, Alferov)
• Belarusian SU: 3 (Klimasheuski, Paliukhovich, Filinovich)
• Moscow IPT: LinkCat (Zgursky, Gaponov, Surkov)
• Kazan FU: AJ (Ilikayev, Yagafarov, Kapralov)
• NNSU: 1 (Khlyustov, Ryabchikova, Emelin)
• Tolyatti SU: A (Zakharov, Sabirov, Panin)
• IITU: 1 (Baimukanov, Sardarbekov, Kyzyrkanov)

Also, join the traditional ICPCLive team online broadcast from the site in St. Petersburg. The schedule for both days can be found here.

We have compiled a list of teams grouped by ratings, which will be especially interesting to follow. What are your predictions? Favorites?

Share your impressions and photos on social networks using hashtag #NERC.

Who will represent the Northern Eurasian Region in the ICPC 2021 Final whenever it happens? We will find out this Sunday! Stay tuned!

omg hi!

I am pleased to invite you to participate in Codeforces Round #712 (Div. 1) and Codeforces Round #712 (Div. 2)! You will be given 6 problems and 2 hours 15 minutes to solve them. I'm happy to announce the theme of this round is déjà vu!

I would like to thank the following people:

• antontrygubO_o for accepting all of my problems at gunpoint
• Nika_Tamliani, arvindr9, dorijanlendvaj, I_Love_YrNameCouldBeHere, ssense, _cherry_, TheDramaQueen, Jellyman102, SecondThread, Kuroni, nor, 300iq, evilbuggy, prabhAmbrose, and kpw29 for testing the round and being awesome
• Qualified and FlakeLCR for being the first users to register for the Div. 2 and Div. 1 divisions, respectively!
• MikeMirzayanov for the amazing platforms Codeforces and Polygon!
• You, for upvoting!

Make sure you read all problems, and I'm happy to announce the theme of this round is déjà vu! Good luck, have fun!

The score distribution will be announced immediately because you deserve it ❤️:

Div. 1: 750 — 1000 — 1250 — 1750 — 2500 — 4000

Div. 2: 500 — 1000 — 1750 — 2000 — 2250 — 3000

UPD: Editorial

The contest is over; I hope you enjoyed it! The editorial is available here.

The 9th April Fools Day Contest will take place on Thursday April 1st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

In this round you'll be given several weird problems 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, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020.

Good luck, and have fun!

Hello all!

We are proud to invite you to CodeCraft-21, which takes place on Mar/29/2021 17:35 (Moscow time). It is rated for all Div2 participants (rating under 2100).

This contest comes under Threads'21, as a part of our annual techno-cultural fest Felicity, IIIT Hyderabad. We have special prizes for Indian participants!

You will be given six problems to solve in a duration of two hours.

We have tried our best to keep clean statements, useful samples with good explanations, and strong pretests! We have written step-wise editorials, and will also release video editorials!

We would like to thank these amazing people for helping make the contest happen:

• BledDest for great coordination of our round
• ninja_28, dixitgarg, ltc.groverkss and myself for amazing problemsetting
• madlad, AnimeshSinha1309, shash42, nikhil_c for contributing several important problem ideas
• TheOneYouWant, amnesiac_dusk, awoo, SleepyShashwat, gaurav172, adedalic, amul_agrawal, vasu0403, d_shi, Horcrux1729, RajMaheshwari, menavlikar.rutvij, Arpanet, spashal, Tinkidinki for testing our problemset, and providing very valuable feedback to improve problem statements, sample cases, and pretests
• gaurav172 and shaanknight for giving valuable advice on contest creation
• ahish9009 and harshita_gupta for excellent poster and tshirt design
• And finally MikeMirzayanov for the amazing platforms, Codeforces and Polygon.

There will be an interactive problem! You are recommended to read the corresponding guide.

We hope you enjoy the contest as much as we did preparing it! Good luck!

Update: The scoring distribution is 500/1000/1750/2500/2500/3000.

Update: Editorial is up! Video editorials available on our YouTube channel.

We are sorry for the sudden increase in difficulty from C to D. Nonetheless we hope you enjoyed the problems! :)

PRIZES: The following twenty lucky participants receive a tshirt:

• top 10 Indian participants
• random 10 from top 100 (ranks 11-100) Indian participants

These ranks are determined from the combined unofficial ranklist. We are coordinating with the CF team for the tshirt design, and we'll update the blog post when it is finalized. We also have INR 7K worth prizes exclusively for IIIT-Hyderabad students!

Hello, Codeforces!

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Hello! Codeforces Round #710 (Div. 3) will start at Mar/25/2021 17:35 (Moscow time). You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended 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 7 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 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.

The problems for this round were invented by MikeMirzayanov, Supermagzzz, Stepavly and sodafago.

Thanks to darkkcyan, bugdone, harlequen, iankury, bfs.07, songsinger, infinitepro, sodafago, Gassa, Rox, sharepoLOVEDDD for testing this round.

Thanks to MikeMirzayanov for platforms and coordination of our work. Good luck!

</almost-copy-pasted-part>

UDP: Editorial is ready

Hello Codeforces!

The sixth round of the Kotlin Heroes series recently finished! All the rounds are available to be used for practice here: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round and Episode 6). Thanks to everyone who participated – you inspire us to work even harder on the problems for the next round, and we think you’re really going to like them!

Congratulations to the top three contestants:

1. tourist
2. Egor
3. Tlatoani

A Kotlin Heroes t-shirt and exclusive Kotlin stickers will be presented to:

1. tourist
2. Egor
3. Tlatoani
4. eatmore
5. uwi
6. Benq
7. Geothermal
8. TadijaSebez
9. Maripium
10. Maksim1744
11. pashka
12. Heltion
13. dalt
14. galen_colin
15. tabr
16. SYury
17. natsugiri
18. Golovanov399
19. Spheniscine
20. Discombobulated
21. Ra16bit
22. Aidos
23. yudedako
24. nuip
25. knightL
26. golikovnik
27. wifiiii
28. Fortin
29. majk
30. WiwiHo
31. Bench0310
32. wu_qing
33. Kuyan
34. Nikitosh
35. cjtoribio
36. receed
37. vadimmm
38. SecondThread
39. LeoPro
40. rapira
41. Lily
42. nhho
43. PavelKunyavskiy
44. abc864197532
45. tatyam
46. Heart_Blue
47. Ji_Kuai
48. darnley
49. Potassium
50. 353cerega

These participants also won branded t-shirts:

1. polingram
2. Prateek
3. rotavirus
4. linjek
5. pr3pony
6. ostroumov
7. harshrajani460
8. xiaowuc1
9. arvindf232
10. illyakr
11. Jetman
12. Leksiq
13. IceKnight1093
14. procrastinate7
15. man.yasakov
16. Viktor36
17. matvey.kazakov
18. cmplx-xyttmt
19. SourabhYelluru
20. daisy_2000
21. stanm
22. cristian1997
23. SerVB
24. aaronsms
25. chick_magnet
26. Ditmarscehen
27. My_password_is_qwerty123
28. Misha_Help
29. Sohsoh84
30. igla
31. ans_human
32. mystic777
33. __RANI
34. staffle
35. MissNick
36. arpit_malhotra
37. penad
38. I_love_Anya_Prokopyeva
39. son8bon
40. RandYan
41. adimiclaus15
42. babkabass
43. KKT_89
44. nishuz
45. BMking
46. KEKWait
47. Kerpoo
48. pineapple_pasta
49. GlobalElite
50. aka2910

We will contact the winners soon to coordinate the delivery of your prizes!

Special thanks goes to SecondThread for streaming the solutions of the entire practice round. Check out this wonderful tutorial: https://codeforces.com/stream/203

If you are still new to Kotlin but want to give it your all in the next round, take a look at Basic Kotlin (solve Koans), Kotlin Playground, this tutorial, and these videos on competitive programming in Kotlin.

We wish you all the best and hope you enjoy coding with Kotlin!