Hello, Codeforces!

We, DK318 and unreal.eugene, are students of ITMO University. And we have recently joined the developers team of Codeforces and Polygon. We have prepared this round for more careful acquaintance with Polygon. Very soon you will be able to see the first results of our work as developers.

Except us, in round development participated MikeMirzayanov, geranazavr555 and doreshnikov. We hope that you will enjoy the competition!

Codeforces Round 731 (Div. 3) will start at Jul/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 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 7 problems and 2 hours 15 minutes 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.

Thanks to ashmelev, Monogon, CtrlAlt, Tzak, FelixArg, antontrygubO_o, bugdone and brian for testing the round and improving tasks.

Good luck!

UPD 1

Editorial.

Hello Codeforces!

I and DK318, as students of ITMO University, joined the Codeforces team in June. Last month we mainly dealt with the development of the Polygon platform and were focused on one significant feature lots of people dreamed of.

Have you ever made some changes to the problem, and at the same time another person changed the same file? I believe most of you did and disliked this situation. If you wanted to resolve the conflict, you needed to download an archive containing all your changes and repeat them all in the newest revision of the problem. This was very confusing and time-consuming, wasn't it? And now we present probably the most anticipated feature of Polygon since its creation: a web interface for resolving conflicts.

Hello Codeforces!

I am quite excited to invite you to my first ever round, Codeforces Round 730 (Div. 2) which will start on 07.07.2021 17:35 (Московское время). The round will be rated for participants of Division 2 (having rating strictly less than 2100). As always, Division 1 participants are welcome to participate in the round but it will be unrated for them.

The problems of this round will be themed on the 2005 video game Need For Speed: Most Wanted. You will be given 5 problems and 2 hours 15 minutes to solve them. One of the problems will be interactive. So, it is recommended to read the guide on interactive problems before the round.

I would like to thank -

• Aleks5d for coordinating the round and not rejecting any of my problems :)
• KAN for reviewing all the problems and providing invaluable suggestions throughout the round preparation.
• towrist and yash_daga for listening to my problem ideas even before I proposed them, providing invaluable suggestions and testing the round.
• Akulyat, andr0901, Mazaalai, talibmohd, nnv-nick, mcdx9524, DimmyT, kassutta, 4qqqq, wxhtzdy, Karavaiev and asrinivasan007 for testing the round.
• amgfrthsp for translating the statements.
• MikeMirzayanov for the amazing Codeforces and Polygon platform.
• All the participants for participating.

I tried my best to create interesting problems with clear statements, strong pretests and useful sample test cases. Make sure to read all of them. Good Luck and Have Fun. See you on the Blacklist ranklist.

The score distribution is here: $$$500-750-1500-(1000+1250)-3000$$$.

UPD: Editorial

UPD: Congratulations to the winners

Div. 1 + Div. 2 -

1. Geothermal
2. Golovanov399
3. SSRS_
4. uwi
5. tfg

Div. 2 -

1. h0up1ngze
2. olmrgcsi
3. nicalvarez
4. LordVoIdebug
5. islingr

First Solves -

A: Geothermal
B: Geothermal
C: olmrgcsi
D1: h0up1ngze
D2: Golovanov399
E: tfg

Hello Codeforces!

feecIe6418 and I are glad to invite you to Codeforces Round 729 (Div. 2) which will start on Jul/03/2021 16:05 (Moscow time). Note the unusual start time of the round.

The contest will last for two hours, and you will have five tasks to solve. The tasks are prepared by feecIe6418 and me. This round is rated for participants whose rating is not higher than 2099.

We would like to thank:

• Aleks5d for coordinating and helping us with the problems.

• dorijanlendvaj, waaitg, Imakf, alexX512, Akulyat, talibmohd, hbarp, andr0901, nnv-nick, Delmos, kassutta, wxhtzdy, 4qqqq, for testing the problems and providing useful feedback.

• amgfrthsp for translating the statement

• finally, MikeMirzayanov for great platforms Codeforces and Polygon!

It's the second time we hold our contest, our previous round Codeforces Round 670 (Div. 2).

We tried our best to make the statements short and clear, pretests strong and problems interesting. We hope you like the problems!

Score distribution will be announced shortly before the round.

Score distribution: 500-1250-1500-2000-(2000+1000)

Editorial is published Editorial

Congratulation to the winners:

Div1+Div2:

1.Nilou_

2.244mhq

3.jiangly

4.Benaive

5.Ormlis

Div2:

1.Nilou_

2.Benaive

3.hehezhouyyds

4.TuNormie04

5.SoilCrystal

Hello, Codeforces!

First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the five Kotlin Heroes competitions which were held previously: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, and Episode 6.

Ready to challenge yourself to do better? The Kotlin Heroes: Episode 7 competition will be hosted on the Codeforces platform on Jun/29/2021 17:35 (Moscow time). The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers.

Prizes:

Top three winners will get prizes of $512, $256, and $128 respectively, top 50 will win a Kotlin Heroes t-shirt and an exclusive Kotlin sticker, competitors solving at least one problem will enter into a draw for one of 50 Kotlin Heroes t-shirts.

Registration is already open and available via the link. It will be available until the end of the round.

The round will again be held in accordance with a set of slightly modified ICPC rules:

• The round is unrated.
• The contest will have 9 problems of various levels of complexity.
• You are only allowed to use Kotlin to solve these problems.
• Participants are ranked according to the number of correctly solved problems. Ties are resolved based on the lowest total penalty time for all problems, which is computed as follows. For each solved problem, a penalty is set to the submission time of that problem (the time since the start of the contest). An extra penalty of 10 minutes is added for each failed submission on solved problems (i. e., if you never solve the problem, you will not be penalized for trying that problem). If two participants solved the same number of problems and scored the same penalty, then those of them who had previously made the last successful submission will be given an advantage in the distribution of prizes and gifts.

If you are still new to Kotlin we have prepared a tutorial on competitive programming in Kotlin and Kotlin Heroes: Practice 7, where you can try to solve a few simple problems in Kotlin. The practice round is available by the link.

We wish you luck and hope you enjoy Kotlin.

Hello Codeforces!

ijxjdjd and I are pleased to invite you to participate in Codeforces Round 728 (Div. 1) and Codeforces Round 728 (Div. 2) which will be held on Jun/25/2021 18:35 (Moscow time). Please note the unusual timing. Each division will have 5 problems and 2 hours and 15 minutes to solve them.

We would like to thank:

• adedalic for amazing coordination of our round!

• singleLOOP, skittles1412, penguinhacker, wxhtzdy, coderz189, dorijanlendvaj, qlf9, Nezzar, Tlatoani, MagentaCobra, Etherite, and prabowo for testing the round and providing invaluable feedback.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon.

• You, for participating!

Read all of the statements carefully, and we hope you enjoy the problems! Wish you high ratings!

UPD: I would also like to thank Roberticey, golions, and 244mhq for testing.

UPD: Here's the score distribution:

Div 1: 500 — 1250 — (1500 + 750) — 3000 — 3500

Div 2: 500 — 1000 — 1500 — 2250 — (2500 + 750)

UPD: The editorial is out!

UPD:

Congratulations to the winners!

Div. 1:

1. maroonrk
2. tourist
3. Radewoosh
4. LayCurse
5. NotaMotuaQAQ

Div. 2:

1. tampa
2. CF_is_my_GF
3. Apple_Method
4. Skybytskyi.Nikita.2
5. -this-is-obd-

Hi!

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 and, of course, Helen Andreeva.

We are happy to announce the Codeforces Round #727 based on the problems of this olympiad! It will be a Div. 2 round, which will take place at Jun/20/2021 13:05 (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).

The problems of this olympiad were prepared by talant, Siberian, shishyando, Artyom123, TeaTime, Tikhon228 under the supervision of grphil.

Thanks to KAN, Aleks5d and isaf27 for their help in organizing the Codeforces version of this contest and 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.

Good luck!

UPD1: Thanks to _overrated_ and Ormlis for testing.

UPD2: Scoring distribution: 500 — 750 — 1250 — 1500 — 2000 — 2500

UPD3: Editorial

UPD4: Winners!

Div. 2:

1. Nilou_
2. newbiewzs
3. tou_xue
4. SoilCrystal
5. EEIEE

Div. 1 + Div. 2:

1. Maksim1744
2. kal013
3. jiangly
4. LayCurse
5. 2qbingxuan

Hello Codeforces!

mesanu and I are very glad to invite you to Codeforces Round 726 (Div. 2) which will take place on 18.06.2021 17:35 (Московское время). The round will be rated for participants with a rating lower than 2100. Division 1 participants are also welcomed to take part in the competition but it will be unrated for them.

The round was originally planned to be a division 3 round so the problems might be slightly easier than average Div 2.

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

We would like to thank the following people:

• 1-gon for amazing coordination of our round!

• antontrygubO_o for testing, translating statements and providing useful ideas!

• Maksim1744, Ari, qpwoeirut, magnus.hegdahl, PurpleCrayon, Brodicico, Omkar, DenjellBoone, Arsenie, Lost_Arrow, Etherite, asrinivasan007, nishuz, cringeworthyplayz, Nika_Tamliani, Vpurice for testing and providing invaluable feedback!

• MikeMirzayanov for great Codeforces and Polygon platforms!

• You, for participating!

The scoring distribution is: 500 — 750 — 1000 — 1500 — (1250+1750) — 2000.

UPD: Editorial

Hello everybody!

After a long break I would like to announce the fourth Bioinformatics contest organized by ITMO University, Bioinformatics Institute, Rosalind and Stepik. The contest is sponsored by JetBrains, Yandex, Serokell, and Genotek.

The contest is hosted on Stepik platform. To participate you have to sign the rules.

The contest consists of two rounds:

• The Qualification round is already started today. It will be open until June 19 11:59 UTC+0.
• The Final round will be held for 24 hours starting at June 26 13:00 UTC+0.

The contest is prepared by the following team: Alexey Sergushichev, Nikita Alexeev, budalnik, demon1999, tourist, cdkrot, GShark, doreshnikov (all ITMO University), German Demidov (Center for Genomic Regulation), Andrey Prjibelski (CAB SPbU).

Are there any prizes?

• 1st place – Whole Genome Sequencing
• 2nd and 3rd – Whole Exome Sequencing
• 4th and 5th – 23andMe or Genotek DNA Service
• 1st–30th – Honorable Bioinformatics T-Shirt

Do I need to know biology?

The knowledge of biology is not necessary to solve the problems!

We wish that you will like the problems!

Good luck!

Hello, Codeforces!

Welcome to the Codeforces LATOKEN Round 1 (Div. 1 + Div. 2) supported by LATOKEN, that will start on Jun/13/2021 18:35 (Moscow time). It will be a combined rated round for both divisions (and div 3). Please, note the unusual start time.

All problems were created by Aaeria, crackersamdjam, Dormi, Ninjaclasher, and Plasmatic.

We would like to thank:

• Valentin Preobrazhenskiy from LATOKEN supporting the round.
• 300iq and KAN for coordinating the round and answering our relentless questions.
• arvindr9, Delmos, duality, coderz189, wxhtzdy, PurpleCrayon, kalki411, socho, wleung_bvg, and Zeyu for their invaluable advice and suggestions.
• MikeMirzayanov for great systems Codeforces and Polygon.

You will be given 8 problems and 180 minutes to solve them. This contest features at least one interactive problem, so we recommend reading the guide of interactive problems before the contest.

We hope that statements are short and pretests are strong and that you find the problems interesting! Good luck, have fun, and we wish everyone high ratings!

The scoring distribution will be announced closer to the beginning of the round.

Thanks to LATOKEN, winners will get awesome swag:

• 1st place = MacBook Air M1 + Job offering and Stock Options
• 2nd place = Xiaomi Mi 11 + Job offering and Stock Options
• 3rd place = Xiaomi Mi Notebook Pro 15" Enhanced Edition + Job offering and Stock Options
• 4th-10th place = Job offering and Stock Options + Merchandise Pack
• 11th-55th place = Merchandise Pack

Random 10 participants outside of top-55, who solved at least one problem and participated in rated Codeforces rounds before, will get a t-shirt!

A few words from the LATOKEN team:

We welcome you to the intellectual battle between the best coders from around the world! LATOKEN strives to make trading crypto as easy as having a social media account. We are always looking for the best of the best to join our team. As a result, LATOKEN is currently in Coingecko’s Top 15 with over 600 000 app installs within just one year from its launch and 1m+ users in total. The emerging blockchain based financial systems will open exciting opportunities, because crypto is fully global and mostly independent of conservative banks.

If you want to become a part of something bigger, work remotely with a team of international professionals and change the world, contact our recruiters for internships and employment opportunities in the LATOKEN team. Use our bot or fill out the form below and tell us a little about yourself.

UPD: The scoring distribution is 500 — 1000 — 1250 — 1500 — 2250 — (1750 — 1250) — 3250 — 3500.

UPD: Editorial

Congratulations to the winners:

1. Benq
2. tourist
3. Radewoosh
4. Endagorion
5. ecnerwala
6. heno239
7. VivaciousAubergine
8. gamegame
9. Pyqe
10. maroonrk

The prizes will be distributed in the next few days after we remove cheaters.