Hi Codeforces!

Sorry for being late for the announcement.

I'm glad to introduce to you my first contest Codeforces Round 482 (Div. 2). It will take place on May/14/2018 17:35 (Moscow time).

You will have 5 problems and 2 hours to solve them.

The problems were prepared by me (Quyen Dinh), Kuroni (Trung Dang) and Shirone (Lam Le) with suggestions from FallingStar (Nhat Hoang) and HaiDang2001VN (Dang Huynh). I would like to thank KAN for his great help in checking the problems and giving comments, Tommyr7 for testing all the problems and MikeMirzayanov for the awesome Codeforces and Polygon platform.

Note that the round is rated for everyone with rating below 2100.

In this contest, you will meet Kuro, Shiro and Katie, the three naughty but smart cats who love asking thought-provoking questions. I hope you will find our problems interesting. Good luck to you all!

UPD: Also big thanks to cyand1317 for helping us with the problems and arsor for translating the problems into Russian. Sorry, I forgot you guys.

UPD2: The scoring distribution is 500 — 1000 — 1250 — 1750 — 2250. Have fun!

UPD3: Congratulations to the winners!

Div. 1 & Div. 2:

1. dotorya

2. mama_budra

3. coach.31

4. nuip

5. kevinsogo

Our top 5 solved all the problems. Awesome!

Official:

1. mama_budra (solved all problems!)

2. coach.31 (solved all problems!)

3. Illidan

4. ranwen

5. iloveUtaha

Thanks for everything! Here is the editorial.

Hello!

Codeforces Round 481 (Div. 3) will start on May/13/2018 12:05 (Moscow time). It will be the second Div.3 round in the history of Codeforces. You will be offered 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.

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.

The problem are written by me and fcspartakm. Many thanks to testers AGrigorii, BigBag, nhho and Sert!

Good luck!

UPD 1: Thank you for participation. Problem tutorials have been published.

UPD 2: Congratulations to the winners! Top-5 (official standings):

• AntonD
• pedulia
• liyingyan7
• luhong
• Silver-Water

Harbour.Space University, the International Tournament of Young Mathematicians (ITYM) and Moscow Institute of Physics and Technology (MIPT) are proud to announce a special high schooler's online test, May 26th at 15.00 CET Time. The test will gauge your level in both maths and computer science and give a chance to win two weeks in a math and computer science summer camp for gifted youth Tech Scouts, taught in English for ages 12-18, held 16-29 of July in Barcelona, Spain.

You can take part in the online test if all the following conditions are met:

1. Between the ages of 12 to 18,
2. Have not graduated high school,
3. Eligible to take part in IOI/IMO 2019.

The top performers of the online contest will be invited for a personal interview to demonstrate understanding of the problems solved during the contest. After the test, the 100 most successful performers will be interviewed, and the top will be awarded a full tuition waiver to attend the advanced level of the Technical Track of Tech Scouts.

Tech Scouts is designed to lay out the foundation of knowledge in mathematics and computer science for the next phase of higher learning. During a two-week intensive training, the students will follow a college level curriculum and discover their passions by getting to know one of Europe’s leading institutions in design, entrepreneurship and technology.

In order to register for the contest, please fill out this type form before 11.59pm May 24. All participants of the contest will get a 25% discount promo code to attend Tech Scouts.

Register

UPD For those of you who cannot meet the required conditions, but would still like to participate, please fill out this form

UPD2 As many of you have informed us of the date coinciding with Google Code Jam round 2, we are moving the date by one week. The new date is May 26. Thank you, everyone!

Hello, Codeforces!

The international competitive programming boot camp Moscow Workshops ICPC is inviting participants! This summer the training program is hosted in different parts of Eurasia on the same dates: July 23-30 2018.

!

Moscow Workshops ICPC boot-camps are preparing the winners of the ICPC championship: teams who participate in Moscow Workshops events achive the highest results at ICPC World Finals, for instance this year 10 out of 13 teams who won medals at the World Finals were participants of Moscow Workshops ICPC boot-camps.

«Discover Grodno» will be held for the second time on the base of Yanka Kupala State University, the main training platform for competitive programming in Belarus.

«Discover Vladivostok» will be held for the first time. The hosting university will be Far Eastern Federal University. The smart campus of the innovative FEFU is located on the Pacific coast, it’s beautiful environment will inspire students to show impressive results.

During the 8 days of Moscow Workshops ICPC program students’ teams all over the world will prepare intensively for the biggest and the most prestigious competitive championship. Participants will be able to choose between Division B and Division C depending on their skill level.

Division B is for the students who are preparing for the next ICPC season and other international competitions in programming, the training program will be in English.

Division C is for the newcomers to the world of competitive programming and the it’s program will be held in Russian.

The participation cost depends on the date a payment was made and on the region: citizens of the Eurasian Economic Union (EAEU) countries pay in Rubles and others pay in US dollars:

Until June 15 — 23.000 Rubles (for EAEU), $390 USD From June 16 — 27.000 Rubles (for EAEU), $470 USD

The price includes educational program, accommodation on university campuses, meals and sightseeing tour in spare time.

Join Moscow Workshops ICPC! Good luck!

Hello everyone!

I would like to invite you to participate in Codeforces Round 480 (Div. 2), it will take place tomorrow, May/08/2018 18:05 (Moscow time).

The round consists of 6 problems and you will have two hours to solve them.

The problems were prepared by me with great help from linkinu and Reem. I would like to thank KAN for his great efforts in reviewing the problems and for his suggestions, it is really amazing to see the work done behind every round. Also thanks to Tommyr7, Livace and mike_live for testing the problems, and to arsor for translating the statements into Russian.

This is my first round on Codeforces, I hope that you will find some interesting problems for you.

Note that the round is rated for everyone with rating below 2100.

Good luck and have fun!

UPD: Congratulations to the winners:

Div. 2:

1. phongthan

2. allllekssssa

3. veterfrank

4. lagin

5. Fekete

Div. 1+2:

1. eddy1021

2. phongthan

3. Andreikkaa

4. step_by_step

5. cerberus97

UPD1: Editorial

Hello!

Codeforces Round 479 (Div. 3) will start on May 6 (Sunday) at 14:05 (UTC). It will be the first Div.3 round in the history of Codeforces. You will be offered 6 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.

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 Neon for testing the round.

UPD: Thanks a lot to testers dreamoon_love_AA, eddy1021, step_by_step and Egor.Lifar who agreed to test the problems and found the mistakes. Now we are ready to start the round!

I hope that you will like the problems. If suddenly something does poorly with difficulties of the problems, then we will adjust the difficulties in the next Div. 3 rounds.

Briefly about myself. My name is Vladimir Petrov, I am studying at the 3rd year at Saratov State University and from the high-school I am studying at SSU Olympiad Training Center. In ICPC I participate in the team "Saratov SU Daegons" with awoo and Neon. I like reading and watching science fiction. I’ve read "Song of Ice and Fire" 3 times and wait for publication of 2 more volumes.

Good luck!

UPD2: Editorial

UPD3:

Congratulations to the winners (official results):

Congratulations to the best hackers:

97 successful hacks and 297 unsuccessful hacks were made in total!

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

Hi Codeforces,

As I mentioned before, as part of my Master's thesis, besides my book I am organizing a contest with exclusively geometry problems to showcase some types of problems or techniques that I think could be cool to see in the future in ICPC and other contests.

It will take place this Sunday 08:00 UTC in the Gym (the link will be http://codeforces.net/gym/101793, registration should open 6h before and remain open during the contest). There will be 4 problems to solve in 3 hours.

The problem should be particularly relevant for students participating to the ICPC. But the problems will be very hard, so I think they can be interesting to everyone with a sufficient level in geometry.

The problems will be roughly sorted by estimated difficulty, but please read all the problems, as you might find that you feel more interested by one of the "harder" problems. The statements will be given all together in a PDF attachment. The samples will be in the PDF as well as on the problem pages.

Since it's my first time organizing a whole contest by myself, I hope everything will go smoothly. I would like to thank yunoac for the precious feedback on the tasks (and of course his amazing support during my whole thesis), Nicolas16 for beta-testing the problems in a tight schedule, and of course MikeMirzayanov for the great Codeforces and Polygon platforms.

I hope many of you will participate to the contest and enjoy the problems. See you for the editorial!

PS: You might want to revise your 3D geometry. ;)

UPD: The length is confirmed to be 3 hours. The contest will be held under ICPC rules. You can participate either individually or in a team.

UPD2:

Congratulations to the winners:

1. Team TooLazyToPropagate (hitman623, DeshiBasara, TooDumbToWin)
2. Hujiwara
3. aid
4. chemthan
5. Swistakk

who also happen to be the only participants to solve at least one problem.

Thanks to everyone for participating, the editorial is coming in a moment!

Hello, Codeforces!

It's time for news. I hope you will enjoy!

• We reduce the rating bound for the orange color. Thus, now the orange rating (and the Master title) will start from 2100 rating units.

• The lower bound of the rating for legendary grandmasters is increased to 3000 rating units. Thus, right now in the community, 14 participants meet this requirement. Real legends!

• For rounds like "Div. 2 Only" the upper bound of the rating for official participation is increased. Now everyone whose rating is less than 2100 (i.e., before masters) will be able to register for such rounds to participate officially, their rating will be updated based on the results of the round. We do not plan to increase the complexity of Div. 2 rounds. Practice shows that the problems of such rounds are interesting and useful for participants "below the orange".

• For parallel Div. 1 and Div. 2 rounds we don’t change the rating bound between divisions. So Div. 1 edition of the round continue to include participants with the rating from 1900 and above.

• As an experiment, we plan to host rounds of simplified complexity (Div. 3). In such rounds, the official results will include participants with ratings less than 1600. We plan to include in these rounds simple training problems that will help beginner participants to gain skills and to get new knowledge in a real contest. Since even in the Div. 2 rounds regularly some Div. 1 users register new account and take high place, we also expect such unsportsmanlike behavior in the Div. 3 rounds. We will exclude from the official standings of Div. 3 rounds and put in a separate rooms all those who can’t be reliably called to be a real participant. Accounts that materially participated in less than 2 rating rounds (materially means solved at least one problem there) before the start of the Div. 3 rounds, and those who have ever gained 1900 or more rating units will not get into the official standings and will be assigned to separate rooms. However, this does not mean that there is no rating recalculation for them. Thus, the rating will be updated for all users whose rating is strictly less than 1600 at the time of the start of a round. Perhaps we will experiment with the definition of who should be considered a reliable Div. 3 participant. And thanks to VLamarca for the post about idea of Div.3 rounds!

Updating the boundaries of ratings and changing colors is not an instantaneous process. For this reason, the website may still have outdated information for some time. We are working to apply the announced changes during the day.

I hope you enjoy this news.
— MikeMirzayanov