Hello Codeforces!

We are glad to invite you to Codeforces Round 668 (Div. 1) and Codeforces Round 668 (Div. 2), which will take place on Sep/06/2020 17:35 (Moscow time).

The problems were created by Ari, Kuroni, JettyOller, Monogon, antontrygubO_o and hugopm.

We would like to thank:

• dorijanlendvaj, Jatana and enoone for helping with the preparation of the tasks.

• gamegame for always being nice and supportive.

• DatVu, JettyOller, MofK and atoiz for stealing the round #666, forcing us to retheme around ponies.

• Monogon for making the author list more colorful.

• redblossom, thenymphsofdelphi, qlf9, mcfr, Tlatoani, aohkgnadnart_, McDic, cup_of_tea, bestial-42-centroids, Noam527, Mbfibat, wolfris, ffao, Falseeee, fpc_coder and fivefourthreeone for testing.

• MikeMirzayanov for the Codeforces and Polygon platforms.

There will be 5 problems in each division and will be given 2 hours to solve them (or post memes in the comments if you can't solve any).

We tried to make interesting problems, short statements, useful samples and strong pretests, and we hope you will like it.

Scoring will be announced shortly before the round and editorial will be posted shortly after the round (it is already written).

Good luck!

UPD: The number of problems is now 5 in each division.

UPD2: Score distribution:

• Div.1: 500 — 1000 — 1500 — 2250 — 3000
• Div.2 : 500 — 1000 — 1750 — 2250 — 3000

UPD3: Editorial is out

UPD4: We are sorry for problem div1E being well-known. No setter or tester have seen this problem. We apologize and hope you still enjoyed the contest.

UPD5: Congratulations to the winners:

Div.1

1. maroonrk
2. ainta
3. ko_osaga
4. Itst
5. hos.lyric

Div.2

1. minhchauxinhdep1234
2. potato167
3. guangmutianwang
4. w_o_kje
5. veckoper

Hello, Codeforces!

I'm glad to invite you to Codeforces Round 600 (Div. 2), which will be held on Nov/16/2019 17:35 (Moscow time). It will be rated for all participants with rating below 2100. You will be given six problems and two hours to solve them. As usual, the score distribution will be announced shortly before the round.

The problems were invented and prepared by me. Huge thanks to:

• faremy for taking time to solve and give me precious feedback on most of the problems I have considered putting into my round throughout its whole creation (more than 6 months!)

• 300iq for coordinating the round and giving helpful advices

• MikeMirzayanov for great systems Polygon and Codeforces

• dorijanlendvaj, McDic, nvmdava, Kuroni, fedoseev.timofey, budalnik, _overrated_, aneesh2312, arthurconmy, Ifugao, sdssudhu, Savior-of-Cross, cfalas, teekteek and Ashishgup for testing

This is the first french round on Codeforces, I hope that everybody will enjoy it :) GL&HF to all!

UPD1: Scoring distrubtion is 500-1000-1500-1750-2250-2750

UPD2: Editorial is out

UPD3: Thanks for participating! Congratulations to the winners:

Div.1 (unofficial) participants

1. Um_nik (solved all problems in 38 minutes!)
2. dreamoon_love_AA
3. mango_lassi
4. imeimi
5. cerberus97

Div.2 participants

1. Son
2. root_power_6
3. Do-Kwon
4. AlineSH
5. Hezx

First solve

• A. teapotd (2 minutes)
• B. nitrousoxide (7 minutes)
• C. saketh (4 minutes)
• D. Marisa (8 minutes)
• E. tfg (14 minutes)
• F. Deemo (30 minutes)