UPD: Thanks to Daria ZeroAmbition Stepanova, Mikhail PikMike Piklyaev and Artem Rox Plotkin for help with round preparation!

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Hello! Codeforces Round #595 (Div. 3) will start at Oct/22/2019 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. 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.

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Hi,

We would like to invite you to participate in the live (with 30-minute delay) online mirror contest of The 2019 ICPC Asia Jakarta Regional Contest (our regional website, our regional in ICPC website, official contest portal) this weekend. The online mirror contest will start on Oct/27/2019 06:30 (Moscow time).

The contest consists of several problems and you can solve them in 5 hours.

See you on top of the leaderboard.

Hi everybody,

This Sunday there will be a XVII Moscow Team Olympiad, high school students competition based in Moscow that is an elimination contest for All-Russian Team Olympiad. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Open Olympiad, Moscow Olympiad for Young Students and Metropolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583).

Round will be held at Oct/20/2019 12:05 (Moscow time) and will last for 2 hours. Each division will have 6 problems.

Problems are prepared by wrg0ababd, grikukan, DebNatkh, grphil, voidmax, V--gLaSsH0ldEr593--V, volcolac, Sehnsucht, isaf27, _kun_, Flyrise, Nebuchadnezzar, platypus179, Endagorion under my supervision with great help of GlebsHP, _meshanya_, Endagorion, Zlobober and Helen Andreeva.

Thanks to _kun_ for the round coordination and statement translation, and also thanks for MikeMirzayanov for systems codeforces and polygon, which was used to prepare problems of this olympiad.

Good luck everybody!

UPD1: Winners!

Div. 1:

1. tlwpdus
2. rhrnald
3. ainta
4. dorijanlendvaj
5. wxhtxdy
6. maroonrk
7. djq_cpp
8. QWE_QWE
9. Marcin_smu
10. 300iq

Div. 2:

1. lolkekaidarbek
2. qdd
3. mathusalen
4. conan1412yang99
5. fauzdar65
6. DeepThought42
7. mikeleven
8. AnnieCai
9. liuandi
10. jyf111

Editorial will be published soon.

UPD2: Editorial

Hello, Codeforces!

I'd like to invite you to take part in Codeforces Round #593 (Div. 2). It will held on Oct/17/2019 16:35 (Moscow time). The round will be rated for the participants with rating lower than 2100.

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

Scoring distribution: 500—1000—1000—1750—2000—2500.

The problems of this round were developed by me. Thanks a lot to isaf27 for his excellent coordination, to Mike MikeMirzayanov Mirzayanov for Codeforces and Polygon platform, and to marX, antontrygubO_o, NIWIS, win11905 for testing.

This is my first round ever. I hope everyone will enjoy it.

Good luck!

UPD: The round is over! Congratulations to the winners:

Div.1 + Div.2 participants:

1. LayCurse
2. nuip
3. Geothermal
4. liouzhou_101
5. Pelmelnik2

Official participants:

1. Pelmelnik2
2. lrvideckis
3. zml
4. DAL_DAL_USHEL
5. phosphoric

UPD: Now the Editorial is available.

Hey!

On Oct/16/2019 17:35 (Moscow time) we will host Codeforces Global Round 5.

It is the fifth 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 round will last for 2 hours 30 minutes, 8 problems are waiting for you, and one of them will be proposed in two versions.

Scoring distribution: 500 — 750 — (750 + 750) — 2000 — 2500 — 3000 — 3750 — 4000

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 the whole series get sweatshirts and place certificates.

The problems of this round were developed by me, and here is the list of people who can't take part in the round as they know the problems beforehand:

KAN, Endagorion, arsijo, Rox, lperovskaya, Aleks5d, Learner99, MikeMirzayanov.

Coincidentally, this is also the list of people I'm thankful to for making this round what it is.

The round will be perfectly balanced. As all things should be.

Welcome!

UPD: The round is over! Editorial is here. Congratulations to the winners:

1. Radewoosh
2. Petr
3. 300iq
4. ecnerwala
5. RomaWhite

Hello, Codeforces!

I'd like to invite you to Codeforces Round #592 (Div. 2). It'll be held on Sunday, October 13 at 12:05 MSK. Note that round starts in the unusual time!

The round will be rated for the participants with rating lower than 2100. The statements will be available in Russian and English.

This round is held on the tasks of the regional stage All-Russian Team Olympiad of Informatics 2019/2020 year in city Saratov. The problems were prepared by Ivan BledDest Androsov, Vladimir Vovuh Petrov and me.

Great thanks to Ivan isaf27 Safonov for helping in preparing the contest, to Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platform and to Ivan CaseRuten Khudoshin, Ivan Ivan19981305 Georgiev, Leonid Peinot Mironov, Anton anon20016 Lebedev, Ksenia Pavlova Pavlova and Dmitriy dmitrii.krasnihin Krasnihin for writing solutions.

You will be given seven problems and two hours to solve them. The scoring distribution will be published soon. Good luck everyone!

UPD The scoring distribution 500-1000-1500-1750-2500-2500-3000

UPD Editorial

Hi Codeforces!

Unfortunately, ill-wishers thwarted the round by making DDOS on our infrastructure. Neither the coordinator nor the writers of the round are subjects to blame for the failure. Please do not downvote the announcement of the round. I think that this situation is an additional reason to support the writers. They worked hard and prepared good problems!

Apparently, such an attack should be regarded as a symptom of the fact that Codeforces outgrew the youth phase and entered serious adult life. Of course, we will respond with adequate measures to protect ourselves from such incidents. Fortunately, for almost 10 years of work, a large community has formed around those who care about Codeforces. We are not worried about possible additional expenses or efforts. We can do this. The rounds must go on.

— MikeMirzayanov

UPD 1: All three of today's rounds will be unrated.

UPD 2: Hooray! Today we've survived another DDOS attack. The round was not perfect, but it was not ruined!

Hello Codeforces!

On Oct/08/2019 17:35 (Moscow time) Educational Codeforces Round 74 (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 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 Ne0n25 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:

Hello Codeforces,

First of all, thank you for the great feedback on our survey from the last Educational Round. Over 300 people participated, and we hope to start implementing some of your suggestions really soon.

We also wanted to let you know that we have extended the deadline for our fully-funded scholarships for Masters programs in Bangkok.

Remember, they cover the entire tuition fee as well as the cost of living expenses, so If you or someone you know are interested in technology, entrepreneurship, or design, and believe you have what it takes, we want to hear from you!

Last, but not least, we would like to recommend an article published in our blog last week about the “Top 5 Soft Skills Every Developer Has to Have”. What do you think, do you agree with this list?

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is out

Hi all!

This weekend, on Oct/06/2019 18:05 (Moscow time) we will hold Codeforces Round 591. It is based on problems of Technocup 2020 Elimination Round 1 that will be held at the same time.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at Technocup 2020 website and take part in the Elimination Round.

Div. 1 and Div.2 editions are open and rated for everyone. Register and enjoy the contests!

The Elimination Round authors are BledDest, MikeMirzayanov, Ne0n25, PikMike, Roms, adedalic and me. This round would also be not possible without the help of our testers: KAN, chemthan, gisp_zjz, Kallaseldor, JeffreyHo, danya.smelskiy, Juve45, thank you so much!

Have fun!

UPD.

Unfortunately, the round is unrated.

Tutorial.