# (romanian ioi selection 98, topcoder 2004) Find a permutation p of n elements which maximizes k so that p^k(i) = i for all i in {1..n}.
# [1] 6 people are at a party. Each two persons can be either friends or enemies. Prove that there is at least a group of three mutual friends or a group of three mutual enemies.
# (acm.sgu.ru) How many length n black/white circular necklaces are there? (babb is the same with bbab because the first necklace can be rotated to align with the second one)

Some math books useful for programming competition entusiasts:
[1] Ioan Tomescu "Probleme de combinatorica si teoria grafurilor"
Every year during my highschool there was at least one problem in the national olympiad or in the ioi team selection tests from this book.