Hello, Codeforces!

Today is the first day of the spring and it's great!

Educational Codeforces Round 9 will take place on 01 march 2016 at 18:00 MSK for the first and the second divisions. You can read about educational rounds here and here. I should again notice the high density of contests and championships.

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The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.

It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks.

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The problemset again was totally suggested by Codeforces users. The problem А again was suggested by user unprost (be ready to see a long problem statement). The problem D suggested by Denis Bezrukov pitfall. Alexey Chesnokov CleRIC sent the problem E a long ago. The problems B, C and F was suggested by Lewin Gan Lewin.

Thanks a lot to them and all others who are sending the problems or just ideas of the problems!

The problems was prepared by me (Edvard Davtyan). Thanks to Maria Belova Delinur for checking the English statements. The problems was tested by the same users who suggested them: unprost, Alexey Chesnokov CleRIC and Lewin Gan Lewin. Thanks a lot to all of them!

I hope you will enjoy the problems!

Good luck and have fun!