Hello everyone!

Codeforces round #385 will take place at the unusual usual time of Saturday, 17 December 19:35 MSK.

Thanks to the following people for making this round possible.

• LiChenKoh, xiaowuc1 for helping develop problems and discussing ideas with me.
• winger, AlexFetisov for testing the problems
• GlebsHP for all his valuable help with the round.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

As usual, contestants will have 2 hours to solve 5 problems. Hope you will enjoy the problems!

Scoring will be announced closer before the round.

EDIT: It may be helpful to read the Interactive Problem Guide before the round for both divisions.

EDIT 2: The scoring distribution will be unusual:

Div2: 500-1000-1500-2250-2750

Div1: 500-1250-1750-2250-2500

EDIT 3: While you wait for system testing, here is a quick editorial: http://codeforces.net/blog/entry/49126

EDIT 4: Congratulations to the winners!

Div1:

1. tourist
2. Petr
3. PavelKunyavskiy
4. YuukaKazami
5. W4yneb0t

Div2:

1. Akulen
2. RVS
3. tpablo
4. theodor.moroianu
5. YouAndI

BSUIR Open Archives (polygon contests packages and statements)

• 2019-2020 10th BSUIR Open Programming Championship. Semifinal (blog)

• 2018-2019 9th BSUIR Open Programming Championship. Final (blog)

• 2018-2019 9th BSUIR Open Programming Championship. Junior

• 2018-2019 9th BSUIR Open Programming Championship. Semifinal

• 2017-2018 8th BSUIR Open Programming Contest. Final (blog)

• 2017-2018 8th BSUIR Open Programming Contest. School final

• 2017-2018 8th BSUIR Open Programming Contest. Semifinal

• 2016-2017 7th BSUIR Open Programming Contest. Final (blog)

• 2016-2017 7th BSUIR Open Programming Contest. Semifinal

• 2015-2016 6th BSUIR Open Programming Contest. Final (blog)

• 2015-2016 6th BSUIR Open Programming Contest. Semifinal

• 2014-2015 V BSUIR Open Programming Championship (blog)

• 2013-2014 BSUIR Open Programming Championship. Final (blog)

Hello, Codeforces community!

Codeforces Round #384 for the second division will take place on Wednesday, 14 December 17:35 MSK. Traditionally, first division participants will be able to take part out of competition.

Round was prepared by Yury hloya_ygrt Shilyaev and me, Kirill kefaa Gulin.

Many thanks to Nikolay KAN Kalinin for his help with the contest preparation and Mike MikeMirzayanov Mirzayanov for the Codeforces and Polygon systems.

You will be offered 5 problems and 2 hours for solving them.

Scoring will be announced closer to the beginning of the round.

UPD: Scoring is 500 — 1000 — 1250 — 2000 — 2500

UPD2. The contest is over! Hope you enjoyed it :)

Editorial

Congratulations to the winners!

Div2:

1. TheBartender

2. Ownz

3. lesskreker

4. xyt520

5. SpinyAnteater

6. y32M-71693993

7. ezLadder

8. tqyaaaaaaaang

9. Fiks_warrior

10. 00001

Div.1:

1. Um_nik

2. kmjp

3. Temirulan

4. zscoder

5. rajat1603

Code Festival 2016 was held in Tokyo on 25-30 of November. Boris qwerty787788 Minaev has shared with us his impressions, and Maxim Zlobober Ahmedov and Nicolay KAN Kalinin shared photos.

— To start with, let's mention that, AtCoder and Indeed company announced the festival. How many quals were there? In what way were they arranged?
— There were 3 contests, in which you could take part. In the first part TOP-10 were selected, in the second one — TOP-5, the third one — TOP-5. To sum up, there are 20 foreigners to be selected.

— Which quals the Japanese had then?
— Probably the same, but 200 participants passed the qual there.

— That means, the event is more orientated on Japanese people?
— The previous years the event was held only for Japanese, this year they decided also to invite some foreigners.

— How long did the contest lasted?
— It was quite short. To pass it you had to solve all the problems. It turned out that in first 15 minutes the first 3 out of 5 problems needed to be hand in, and other two are handed in later — you had to think hard on them. The foreigners had to hand in everything taking into account the penalty time.

— The rules of АСМ?
— Nearly. You don't loose anything for penalty attempts, that means it's possible to submit problems any number of times

— No debugging, no testing — just submit, and that's all?
— Yes, it was possible. In addition they also showed verdict on every test.

— Was it clear from the very beginning that those who passed the samplings would be waited in Japan?
— Yes. They payed for the road — bought the tickets. They fed me a bit during the event. On the fifth day I was invited to the Indeed office. Indeed is the American company, which decided to open an office in Tokyo. For an hour they were talking about what the company is doing, and then there was a diner with the engineers. Five people came, three of them were Russians, who work in Yandex. They were communicating with the Russian-speaking public. They told us, that came to Tokyo because of the desire of traveling.

Organizers provided us with the access to the internet by giving routers including Sim with some already payed traffic. Comment and photo: Maxim Ahmedov

— Is it true that in Japanese offices there are balconies with special plants as a recreation area?
— Exactly in the Indeed office there are no. The engineers said they reconstructed their American office here — they all came from Austin.

The competition was held in a business area of the city, which had huge office buildings made of glass and metal. Comment and photo: Maxim Ahmedov

— How many days did the contest lasted?
— During 4 days, from the early morning, 8 o’clock, till 10 o'clock in the evening. The fifth day was a day off.

Sakura blossoms even in winter. Comment and photo: Nicolay Kalinin

Hello all.

This coming February of 2017 will be a new experience for me: I'll be one of the coaches who will teach at the Barcelona ACM-ICPC Bootcamp hosted by Harbour.Space University. In addition, here are some well-known coaches from our community: Endagorion, GlebsHP, Michael, Jacob and snarknews. The camp will be hosted in collaboration with Moscow Workshops ACM ICPC by MIPT. The same proven effective studying techniques will be used at the Barcelona Bootcamp.

For me, it will be the first teaching experience outside of Russia as well as my first trip to Spain. I’ll do my best to coach you how to solve problems in an efficient fashion. Also, it will be an excellent chance to communicate about Codeforces personally with the real users.

Hello Barcelona Programming Bootcamp, in collaboration with Moscow Workshops ACM ICPC, is an opportunity for teams of different levels to prepare for successful participation in ACM ICPC. The Bootcamp will be split in two divisions:

• Division A. Designed to prepare students to excel and win medals in the next ACM-ICPC World Finals.
• Division B. Designed to help teams prepare for the next season of ACM ICPC Regionals and international competitions. This is an appropriate introduction for teams and students new to the world of ACM ICPC and competitive programming competitions in general. The Division B curriculum features thematic lectures and contests.

The participation fee is €1270 per person (cultural programme, accommodation and meals included). The location in Europe gives the effect of the rather high cost. Anyway, the event is non-profitable for these reasons: To prepare world-wide teams for ACM-ICPC and to scale Russian expertise of coaching on other countries.

The Bootcamp will start on February 6th and will last for 9 days to February 14th. If your team (or you individually) is interested to take part, please register before December 24th, 2016 by the link (discount 20% for registration in time):

Register
to Barcelona ACM-ICPC Bootcamp

You can ask any questions by email [email protected]

Hope to meet you on the Bootcamp,
MikeMirzayanov

Hi!

I'm honored to invite you to Codeforces Round #383, it will be held on 6nd December 14:35 UTC. There will be 5 problems for each division as usual. The contest was prepared by AmirReza Arpa PoorAkhavan and Mehrdad Batman Saberi. It's our first official contest at CodeForces.

The contest stories will be about Arpa and Mehrdad and some events happen with them in Arpa's land, in addition you will get some information about Arpa's land and girls living there (Owf (t = 1)).

I'd like to thank myself (:P) and Mehrdad at first, then Nikolay KAN Kalinin for helping me in preparing problems and Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platforms.

The scoring distribution will be announced later.

Answer for one of your common questions : -Yes, It is rated.

UPD. GL & HF. Hope you came up with Dokhtar-kosh solutions for our Dokhtar-kosh problems.

Urgent information from MikeMirzayanov: due to hardware issues, the round is moved to Tuesday 6th December, 14:35 UTC. We are very sorry this happened. More information is available in this post.

UPD. Scoring distribution: Div.1 : 500-1000-1250-2000-2500, Div.2 : 500-1000-1500-2000-2250.

UPD. Contest is over, hope you have been Joon-Joon of the round :P

Congratulations to winners:

Div.1:

1 . jqdai0815

2 . mnbvmar

3 . data_h and nuip (WoW :O)

5 . Phronesis

Sepcial congratulations to anta who solved Div.1 E.

Div.2:

1 . gilcu3

2 . toHisDream

3 . Far

4 . shpsi

5 . orz_liuwei

Editorial is ready.

Hello, Codeforces.

This weekend ITMO University in St. Petersburg with Barnaul, Almaty and Tbilisi will host ACM ICPC Northeastern European Regional Contest.

We have 266 teams (thanks to MikeMirzayanov and snarknews for the link) competing for the chance to go to the ACM ICPC World Finals 2017 which is going to take place in South Dakota, USA.

In ITMO University site 106 teams will compete, including ACM ICPC 2016 World Champions and the team that is leading Opencup ranklist.

We have an Instagram account, we will post there some pictures from contest halls and other weekend activities.

If you are not competing in NEERC, you can try to solve the same problems in mirror. It will take place at 8 AM UTC, December, 4.

Contest scoreboard.

Team name	Team member 1	Team member 2	Team member 3	Total rating
SPbSU Base	aid (2765)	ershov.stanislav (2739)	-XraY- (2551)	8055
MIPT Jinotega	zemen (2741)	ifsmirnov (2721)	Arterm (2506)	7968
ITMO University 1	izban (2762)	enot110 (2550)	Belonogov (2545)	7857
Perm SU Indigenous	I_love_Tanya_Romanova (2650)	mmaxio (2576)	KuchumovIlya (2411)	7637
Saratov SU 1	HellKitsune (2537)	danilka.pro (2485)	IlyaLos (2349)	7371
ITMO University 2	budalnik (2450)	YakutovDmitriy (2422)	SpyCheese (2413)	7285
Belarusian SUIR	netman (2571)	andrew.volchek (2318)	teleport (2247)	7136
SPbSU 3	Kaban-5 (2474)	pavel.savchenkov (2431)	tunyash (2226)	7131
Ural FU Charmander	Tinsane (2438)	kb. (2363)	KungA (2262)	7063

Good luck to all participants
NEERCNews

University Innopolis is organizing and holding Innopolis Open, an Olympiad in Informatics for secondary school students (until 19 y.o.). The Olympiad consists of two rounds — online contest and the on-site competition (held at Innopolis, Russia).

Winners of the first round will be invited to Innopolis to take part in the on-site competition. During the Olympiad, all participants will be offered a free of charge accommodation, meals and transfer from Kazan to Innopolis and back.

Winners of the second (on-site) round will receive awards and can be enrolled in Innopolis University without any admission tests.

• The first (online contest) round will start on December 18 at 10.00 a.m. (UTC +3).

• The second (on-site) round will take place on February 25-26 in Innopolis city, Russia.

Registration is open until December 15, 2016. Participation is free of charge.

Please follow the link to register and find detailed information.

Good afternoon!

I've decided to share my thoughts on the round 382.

Of course, it turned upset not only to me, but also to the round coordinator GlebsHP.

In this round the main negative feedback were caused by two problems: 735D - Taxes and 735C - Tennis Championship.

Regarding 735D - Taxes. I do not share the criticism to this problem. In fact, to solve it would be nice to be familiar with Goldbach's Conjecture and better with Prime Number Theorem. These facts are medium-popular in the world of programming contests. Familiarity with them is useful, gives useful insight into primes. It is important: in this problem it was necessary to perform a simple, but nevertheless, additional step to find solution. It seems to me that it's okay to use problems that have a reduction to some popular and semi-popular topics. Otherwise, it is thrown away a huge number problems.

As a summary for this problem. I agree that the problem 735D - Taxes is not an example of the best problem. But it has a right to exist as one of the problems in a round. It can not take a role of any argument in favor of unrated round. I personally, would not include it in my contest. But the fact of the use of the Goldbach's conjecture (and more prime number theorem) is not a reason for me to convict and forbid a problem.

The situation with the problem 735C - Tennis Championship is much more complicated. It is necessary not to mix the two fundamentally different reasons for occurrence of same problems:

• Problems can be matched randomly, inadvertently. Of course, the coordinator and testers always have a critical look on the problem. At the stage of the contest preparation they immediately react if a problem is familiar to somebody. It is important to understand, that huge number of problems have been invented over the years of existence of sports programming. It is physically impossible to be familiar even with a large part of them. No matter how experienced the jury, sometimes, coincidences happen. Note that if the round is not a stage of a championship and its results do not affect prizes the main reasons for participation in it should be self-development and a desire to get a fan from the competition. None of these goals encourage search in Google.

• Deliberate coincidence or reuse of problems, it is a different story. And here it is what happened. This situation is totally unacceptable (educational rounds do not count), it is necessary to fight with it and to respond rapidly to incidents.

As soon as I examined about the incident, immediately called by phone the writer and discussed (and denounced) the situation. I explained the inadmissibility of such cases and their implications. I think Albert made the correct conclusions and will be accurate in future. Unfortunately, I was informed about incident only after the ratings been updated.

Taking into account large number of participants who didn't notice the issue, who solved problems completely independently, who were happy of upset by their rating changes, shared their results in social networks it does not seem respectful to do to them unrated. I share the view that it would be better not to be so, but history has already taken place. Note that if I learned the situation during the round or immediately after, the outcome might be different. I think it's a good idea to report suspected cases through questions to give a chance the coordinator or me react quickly.

As a conclusion, I do not propose to raise the tragedy, coordinators do not despair. The writers, of course, need to understand the responsibility and importance of taking on the role. Thousands of participants come to solve your problems and, of course, expect something interesting and new.

I urge the community not to forget about respect for the work of authors: to prepare the contest is a big and difficult task. The author takes on a difficult role and if a round took place, so the hard way from the idea to the final implementation has done. Please, be grateful for it, say the authors, coordinators and testers, thank you!

Whatever effort the Codeforces team makes, we can not do rounds without the writers. Therefore, we look forward to your problems. Hope to see good and bright rounds here!

Thank you for attention,
MikeMirzayanov