Wellcome to Codeforces Beta Round #24. I'm author to most of the problems today. Something about me: My name is Nedyalko Prisadnikov and I'm a student from Sofia University in Bulgaria. Here are some pictures of me. Many thanks to Mike Myrzayanov and to Artem Rakhov for organizing the contest, writing alternative solutions and some of the problems.
Good luck and have fun!
UPD: