MathDB
A game on a 100x100 chessboard

Source: German Mathematical Competition BWM 2005, 2nd round, problem 1

September 1, 2005
floor functioncombinatorics proposedcombinatorics

Problem Statement

Two players AA and BB have one stone each on a 100×100100 \times 100 chessboard. They move their stones one after the other, and a move means moving one's stone to a neighbouring field (horizontally or vertically, not diagonally). At the beginning of the game, the stone of AA lies in the lower left corner, and the one of BB in the lower right corner. Player AA starts. Prove: Player AA is, independently from that what BB does, able to reach, after finitely many steps, the field BB's stone is lying on at that moment.