Hi, Codeforces!

Educational Codeforces Round 4 will take place on 25 December 2015 at 18:00 MSK for the first and second divisions. You can read about educational rounds here and here. This time a little time has passed since the previous round. Although we planned this round at Monday, we forgot to include it to schedule, so it was appeared only now. So it is the fourth and the last educational round this year.

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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.

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This time the round was prepared only by me, Edvard Davtyan. Thanks a lot to MikeMirzayanov for helping to invent the problems. Also thanks in advance to Maria Belova Delinur who will check English statements, when they will be ready :-)

I think this time the problems is simpler than usually, because at first we have too hard problemset and removed the hardest problem and added very simple problem. I hope you will enjoy the problems and solve all of them!

Also I want to wish you Happy New Year!!!

Good luck and have fun!

UPD 1: The first phase is ended, hack the solutions of your opponents!

UPD 2: The editorial is ready.