Chessboard Problem
Source: ToT - 2001 Spring Junior O-Level #5
August 17, 2011
combinatorics unsolvedcombinatoricsToTTournament of Towns
Problem Statement
On a square board divided into little squares there are rooks that do not attack each other. Then each rook makes one move like that of a knight. Prove that after this is done a pair of rooks will necessarily attack each other.