Hello everybody!

I'm glad to invite you to Codeforces Round #511 which will take place on Sep/21/2018 17:35 (Moscow time).

There will be 7 different problems in total, and 5 problems in each division. You will be given 2 hours to solve them.

The problems are prepared by me (ditoly), FallDream and ACMLCZH.

Thanks to 300iq who helps a lot in the round coordination, vintage_Vlad_Makeev, V--o_o--V, demon1999, isaf27, cyand1317 for problem testing and MikeMirzayanov for the platform.

This is my first Codeforces round. Hope you can enjoy it. Good luck!

UPD: The scoring contribution:

Div.1 : 750 — 1000 — 1500 — 2000 — 2500

Div.2 : 500 — 1000 — 1750 — 2000 — 2500

UPD2: Congratulations to the winners!

Div. 1 :

1. consecutivelimit

2. scott_wu

3. ohweonfire

4. zemen

5. ko_osaga

Div. 2 :

1. Ranvan_Darkholme

2. SqwrIwy

3. senpai_notice_me

4. Egor_Gornak

5. PrinzEugen

UPD3: The editorial is published. There are many things about problem-setting in it. Do not miss it.

Dear Friends!

If you dream of realizing your ideas in new technologies and products used by a third part of the world's population — join Honorcup Marathon. It will be an unrated round for individual participation, as well as for teams of up to three people.

You will develop new method for determining blood pressure. The standard procedure for measuring blood pressure requires about a minute, during which the cuff compresses the artery in the hand. Since the procedure is relatively sophisticated, simpler methods of blood pressure estimation are potentially of great value. We suggest that you learn how to determine blood pressure based on the data from optical methods to determine changes in blood volume in the finger. Perhaps, your proposal will be implemented in one of Huawei products, and thereby help users reduce the risks of heart and vascular diseases!

At stake: high paid internships in Moscow, St. Petersburg or China (including transportation & accommodation expenses if needed). Also we have 9 smartphones for top 9 results:

• 1-3 place: Huawei P20 Pro
• 4-6 place: Huawei P20
• 7-9 place: Honor 10

And, of course, TOP 30 participants will get T-shirts with Honorcup Marathon logo!

We accept solutions before 4th October, 19.59.59, Msc time. Winners will be awarded on 20th of October during the opening ceremony of 1/4 ICPC 2018 in Nagatino, Msk.

We will ask winners to provide the source code and description of the solution; the details can be discussed in a phone call. In case of reasonable doubt about the violation of the rules, we reserve the right to transfer the prize to the next participant. Thank you for understanding!

Don’t miss your chance!

Good luck to all!

On Sep/20/2018 17:45 (Moscow time) Educational Codeforces Round 51 (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, Ivan BledDest Androsov and me.

Good luck to all participants!

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

Harbour.Space University is proud to announce new partnerships for this year’s Hello Barcelona Programming Bootcamp — VTB and Indeed Tokyo, with the addition of team sponsors Phaze Ventures and Spark Labs.

VTB, the largest international bank based in Eastern Europe, continues to be an official partner of our Hello Programming Bootcamp series, adding further quality to the 3rd edition of the Hello Barcelona Programming Bootcamp by bringing their own participants, as well as by supporting top teams from around the world.

Indeed Tokyo is Japan’s branch of the #1 employment website in the world, giving job seekers free access to millions of jobs from thousands of company websites and job boards. As they sponsor for the second year in a row, Indeed continues to offer the best job opportunities to the boot camp participants as they gather in Barcelona from September 26 to October 4, 2018.

UPD: There was a bug in testset and validator for problem F, we are currently fixing the issue. The statement included the correct resrictions. We will rejudge all the solutions as soon as possible. The round can become unrated, we are discussing this at the moment.

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD2: We investigated the issue to get the following results. 10 people were noticeably affected (that took them more than 3 minutes of the working time). Round will surely be rated for other participants. As for the affected participants, we will look into the rating changes and revert them in case they are negative (set the participant into the unofficial participation mode).

UPD3: Editorial is out

Hello, Codeforces!

Codeforces Round 510 (Div. 2) will start at Sep/17/2018 11:05 (Moscow time). The round will be rated for Div. 2 contestants (participants with the rating below 2100). Div. 1 participants can take a part out of competition as usual.

The round will be rated for the Div. 2 participants (for everybody with rating less than 2100). The statements will be available in Russian and English languages.

This round is held on the tasks of the school stage All-Russian Olympiad of Informatics 2018/2019 year in city Saratov. The problems were prepared by awoo, fcspartakm, Neon, BledDest, Roms and vovuh. Great thanks to our coordinator cdkrot for the help with the round preparation! I also would like to thank our testers DavidDenisov, PrianishnikovaRina, Decibit and Vshining.

You will be given six problems and two hours to solve them. Scoring system will be announced traditionally closer to round start. :)

UPD: The scoring distribution is 500-1000-1500-2000-2250-2750.

UPD2: Editorial

Hello, community!

Codeforces Round #509 will be held on Sep/16/2018 13:35 (Moscow time). The round will be rated for Div. 2 contestants. There will be 6 problems for 2 hours. Please, notice that the start time is unusual.

The round will be rated for the div. 2 participants. The statements will be available in Russian and English languages.

The round will start 2 hours after the start of the Qualification Stage, so they will finish around same time. That's why we ask the participants of the Quals to stay silent and don't share the statements of the contest with anyone. Unfortunately, we cannot add all the problems from Quals to the round, it will contain only six problems.

The problems for the official contest were prepared by the guys from the jury in the person of Alex fcspartakm Frolov, Adilbek adedalic Dalabaev, Ivan BledDest Androsov and me.

We also would like to express our gratitude to Anton arsijo Tsypko for coordination of the round and Mike MikeMirzayanov Mirzayanov for the permission to make a mirror and Codeforces and Polygon platforms. Also big thanks to the testers: IlyaLos, Perforator, kuviman, HolkinPV, MaxZubec, stanislav.bezkorovainyi, Karasick for testing.

As usual, the scoring distribution will be announced just before the round.

Good luck!

UPD: Scoring Distribution: 500-1000-1500-2000-2500-3000

UPD2: Editorial

Hello, codeforces!

Because after Round #507 sad men in suits visited me in my flat, this time I won't write about any task from the future. Instead, this blog will be about my own trick. I said "my own," but probably some of you have already heard about it or even figured it out, but I've developed it by myself, so I consider it as my own.

In particular, it's GEOMETRY TIME!!!. But please, don't escape already. I also don't like this topic so much, that's why I really like this trick. Let me tell you a story from one onsite Polish contest, which took place a few months ago. I was thinking about one of the problems, and I've figured out that I had to do some binary-search (on doubles) and then check if a set of half-planes has a non-empty intersection. The answer would tell me in which direction should I turn in the binary search.

Firstly, I grabbed my head, because I've never written an intersection of half-planes. I had my acm library with Errichto's codes inside, but my knowledge in usage of his part was limited to copy-pasting FFT and Rho-Pollard. Not only I, but also Swistakk figured out the thing about binary search and was trying to intersect half-planes normally, but he failed (we still aren't sure why, probably because of precision issues). Then, I reminded myself a task from eliminations to BubbleCup 2017 (you can find it here), which I solved with the mentioned trick.

On Sep/07/2018 17:35 (Moscow time) Educational Codeforces Round 50 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 Vladimir vovuh Petrov, Roman Roms Glazov, Ivan BledDest Androsov, Maxim Neon Mescheryakov and me.

Good luck to all participants!

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

Hi Codeforces!

We are excited to announce our Work & Study Programme, geared towards diving into the worlds of Computer Science, Data Science, and Robotics, while kick starting a fulfilling paid internship with one of our industrial partners!

Required Education:

Degree in Robotics or Computer, Electrical, Mechanical Engineering or related disciplines

Qualifications and skills:

• Hands-on robotic programming
• Ideally experience within the automotive manufacturing sector
• Knowledge understanding of robot control interface with ancillary equipment
• Use of robot simulation packages
• Deep experience with all things robotic, from infrastructure-free autonomy, to ROS, computer vision, and machine learning
• Experience working with robot parts and components, developing robotics devices
• Ability to concurrently manage multiple diverse and often complex issues and / or projects at the nexus of software, sensors, and hardware

If you are interested in this opportunity, APPLY HERE!

Should you be selected, we will invite you to a series of interviews with admissions, and our industrial partners.

Our programmes are both fundamental and practical. Upon joining, you start working with professionals from admired technology, design and communications companies. You will have strong technical and academic support, alongside industrial experience. This is a unique opportunity to benefit from both worlds of education and industry, in one of the most innovative cities Western Europe has to offer.

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is uploaded

Hi everyone!

It has been almost 2 years since I joined Codeforces, and it has been a great journey as a contestant. I now try to take a shot at problem-setting with my friend Mahir83.

With that said, I bring to your attention my new Codeforces Round 508 (Div. 2) that will take place on Sep/06/2018 18:35 (Moscow time). If your rating is less than 2100, this round will be rated for you; otherwise, you can participate out of competition.

I would like to thank Mahir83 for his help with preparing problems, cdkrot & 300iq for coordinating my round and Um_nik, craborac, vintage_Vlad_Makeev, vovuh & BledDest for testing my problems. I would also like to thank MikeMirzayanov for Codeforces and Polygon platforms.

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

Good luck!

UPD: Scoring Distribution: 500-1000-1500-1750-2250-2750

UPD2: Editorial