Sorry for being late for the announcement.
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 FallingStar1709 (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!
UPD2: The scoring distribution is 500 — 1000 — 1250 — 1750 — 2250. Have fun!
UPD3: Congratulations to the winners!
Div. 1 & Div. 2:
Our top 5 solved all the problems. Awesome!
Thanks for everything! Here is the editorial.