Hi!

Tomorrow, at Feb/07/2019 16:35 (Moscow time) we will host Codeforces Global Round 1.

It is the first round of a new series of Codeforces Global Rounds. 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: _h_, simonlindholm, grphil, vintage_Vlad_Makeev, GreenGrape, budalnik, cdkrot and me. Thanks arsijo and cdkrot for their help in the round's coordination, and also majk, pashka, Jeel_Vaishnav, Ashishgup and Jatana for testing the round!

Good luck!

Congratulations to the winners!

1. tourist
2. Um_nik
3. TLE
4. mnbvmar
5. sunset
6. jqdai0815
7. ksun48
8. molamola.
9. snuke
10. fateice

Editorial.

Hi Codeforces!

February 2019 is already on the calendar, which means that I was late with the report for 2018. Better late than never! Let's remember last year.

In 2018, cdkrot, 300iq and arsijo joined the team of coordinators. The work of the coordinators is headed (and is the coordinator of the coordinators) KAN. I really hope that a more measured schedule of preparing rounds by a large team of coordinators will give a better insight into the contests. The main innovations in the platform are implemented by me and the developers kuviman, fcspartakm, MaximShipko. Great work on the organization of events and prizes mailing was done by gKseni.

Special thanks to the writers of the problems and testers. It is your content that charges the community with life and unites all of us. Thank you for the problems!

And now let's summarize the 2018th year.

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!
• VK, VK Cup — team competition for young Russian-speaking programmers with a series of elimination rounds and finals in St. Petersburg
• Mail.Ru, Mail.Ru Cup — open individual programming competition, consists of several stages, Technocup — open competition for schoolchildren
• Harbour.Space University — a series of educational rounds, the selection of summer school Tech Scouts
• Lyft — a two-level competition with the Final at Lyft headquarters (California) and the mirror contest for worldwide participants
• Avito, Avito Code Challenge and Avito Cool Challenge — open partnership rounds targeting a wide international audience
• Microsoft, Microsoft Q # Coding Contest — unusual quantum computing competition
• AIM Tech — open partnership round targeting a wide international audience
• Huawei — research competition (marathon) with elements of machine learning
• IQ Option — private round as a corporate training

Hello!

It is always satisfying and important for me when former contest participants offer their help to the community and support the development of programming competitions. And now I am in a hurry to share the news that thanks to the support of XTX Markets and the personal participation of Yuri Bedny and Alexander Gerko, we are launching a new line of Codeforces Global Rounds. Hooray!

Like many of you, I had never heard of XTX Markets before but it is one of the largest quantitative-driven electronic liquidity providers in the world. I understand little about the financial sector, but with their 34,148 cores and 42 petabytes of usable storage in their research cluster, XTX’s rapid growth and strong market share globally speak for themselves.

So, in 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all authors and problem testers.

I will be very happy for Codeforces to work with the best authors of the problems. I hope that the XTX Markets initiative will allow for interesting and testing rounds that will delight community members! We have the opportunity to pay $800, double fee, for the preparation of a full set of problems (for some rounds we may collect problems from different authors).

The first Global Round will take place very soon — starting Feb/07/2019 16:35 (Moscow time). I hope you will enjoy the round!

— MikeMirzayanov

Hello Everyone!

I would like to invite you to CodeCraft-19, which is a part of Felicity, the annual techno-cultural fest of IIIT Hyderabad. It will take place on 03.02.2019 18:35 (Московское время).

The round will be rated for Div 2 participants (whose ratings are lower than 2100). As usual, participants from the first division can participate in the contest out of the competition. You will be given 5 problems, all of which are based on the theme of our fest, "Superheroes".

I would like to thank the CodeCraft team -- nir123, additya1998, devanshg27, gaurav172, night_fury208, shaanknight, psaini, sharmaritvik60, swetanjal and vivace_jr -- for helping in preparation of the problemset. I would also like to thank KAN and 300iq for round coordination, ----------, Aleks5d and mohammedehab2002 for testing the round and MikeMirzayanov for the great Codeforces and Polygon platforms.

Following the convention, score distribution will be announced shortly before the contest.

Good luck to all the participants!

UPD1: 500-1000-1500-2000-2500

UPD2 Editorial is published! We sincerely apologize for the weak pretests in B and for the difficulty gap from C to D which turned out to be harder than what we expected.

UPD3 Congratulations to the winners!

1. prodakcin

2. Taiyaki

3. yww_AFO

4. Mindstorm

5. ThankGodItsFriday

6. Issh

7. hfctf0210

8. Y.nnnnnnn

9. kirillbogatiy

10. PedyD

Hello, Codeforces!

It's my honor to invite you to Codeforces Round #536 (Div. 2), which takes place at 12:35 UTC, January 31st, 2019. The round will be rated for all division 2 participants (with rating less than 2100). Also we warmly welcome those division 1 participants to join us out of competition.

This is my second round on Codeforces platform, and my first round was on January 31st, 2018, which is such a coincidence that I would like to say thanks to KAN for his awesome coordination and great dedication to this round. Besides, much thanks to testers Aleks5d, cyand1317, mohammedehab2002, ---------- for their excellent testing work. Also, I would like to appreciate the Codeforces platform created and maintained by MikeMirzayanov, without which the round wouldn't be possible.

In order to celebrate the Lunar New Year (or Spring Festival) originated in China on February 5th, I proposed the round with 6 problems, whose theme is about the Lunar New Year. In this round, you are going to help Alice and Bob to solve some problems in the preparation of celebrating the Lunar New Year in 2 hours. I hope that those problems can interest you and improve your programming abilities, at the same time, bring you luckiness as well as high rating in the coming Lunar New Year!

As a convention, the scoring distribution will be announced soon.

Again, wish you more luckiness and higher rating!

UPD1: Editorial is published.

UPD2: The scoring distribution will be 500-1000-1250-1500-2250-3000. Note that there are 6 problems and you will be given 2 hours to solve them.

UPD3: System test is finished. We are sorry for that technical issue which ruined your happiness. Despite the issue, I hope you do learn something from the problem set, which might be far more important than the rating itself. Enjoy problems, and looking forward to the next contest with better problem set to learn something new, which in my opinion is what Codeforces platform wants to provide us with. Thanks for your participation and dedication even after the unrated announcement. :)

UPD4: The real Editorial is published. Thanks for your patience.

UPD5: Despite that the round is unrated, I have to announce the winners, who deserve it because of their hard work.

Div. 2

1. developer227

2. newbieyzr

3. Zharaskhan

4. I_AM_CHTHOLLY

5. mzhmxzh

6. radoslav192

7. Vit.C

8. visitWorld

9. yycdage

10. xuzhiyuan1

11. zhangqingqi

12. Crossguard

13. gtrhetr

14. Itst

15. HwSh

Hello Codeforces!

On Jan/26/2019 18:35 (Moscow time) Educational Codeforces Round 59 (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 extented ACM 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 and me.

Good luck to all participants!

UPD: You can discuss the problems after the contest on a local Discord server.

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

Hello Codeforces!

A quick reminder to check out the Hello Muscat Programming Bootcamp!

Every day, both the Hello Programming Bootcamp and the Moscow ICPC Workshop will be competing simultaneously, 4,000 kilometers from each other — our camp will take place in Oman, from March 9th to March 15th, 2019 — registration is still open for this unique opportunity, so be sure to give it a look, we would love to see you there with us!

And, don’t forget that Harbour.Space University’s opportunity for a fully funded Master’s in Robotics programme scholarship is still open! Head over to their website to see the details, and apply before the registration date closes.

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD2: The editorial is out

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Hello!

Codeforces Round 535 (Div. 3) will start at Jan/23/2019 17:35 (Moscow time). You will be offered 6 or 7 problems 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 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 awoo Piklyaev, Maksim Neon 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.

</copy-pasted-part>

UPD: I also would like to thank testers ismagilov.code, budalnik, Arpa, filippos, eddy1021 for the great help in round preparation!

UDP2: I don't sure about G63-AMG so I included top-6 instead of top-5 in the table. And I'm also don't sure that some hackers aren't cheat so forgive me if my information is wrong.

UPD3: Editorial is published!

Congratulations to the winners:

Congratulations to the best hackers:

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

Hey everyone!

I'm glad to invite you to Codeforces Round 534 (Div. 1) and Codeforces Round 534 (Div. 2), they will start on Jan/22/2019 17:35 (Moscow time). The round will be rated for both divisions.

Problems were prepared by me, Ivan isaf27 Safonov, Denis altruist Anishchenko and Ildar 300iq Gaynullin. Thanks to Um_nik for testing and MikeMirzayanov for the great Codeforces and Polygon platforms.

You will be given five problems in each division and two hours to solve them.

UPD: Score distribution: Div1:500-1000-2000-3000-3500, Div2:500-1000-1500-2000-3000

UPD: Congratulations to the winners!

Div. 1:

1. mnbvmar

2. whzzt

3. aid

4. dotorya

5. TLE

Div. 2:

1. aequa

2. RatingBooster_2

3. ujerpacul

4. Igor_Zakharov

5. halohalo

UPD: Editorial