MathDB
Game on a regular polygon

Source: 7th RMM 2015, Problem 2

February 28, 2015
combinatoricsRMMcombinatorial geometryRMM 2015

Problem Statement

For an integer n5,n \geq 5, two players play the following game on a regular nn-gon. Initially, three consecutive vertices are chosen, and one counter is placed on each. A move consists of one player sliding one counter along any number of edges to another vertex of the nn-gon without jumping over another counter. A move is legal if the area of the triangle formed by the counters is strictly greater after the move than before. The players take turns to make legal moves, and if a player cannot make a legal move, that player loses. For which values of nn does the player making the first move have a winning strategy?