JBMO Shortlist 2020 C1
Source: JBMO Shortlist 2020
July 4, 2021
JuniorBalkanshortlist2020combinatoricsgame
Problem Statement
Alice and Bob play the following game: starting with the number written on a blackboard, each player in turn changes the current number to a number , where is a prime divisor of . Alice goes first and the players alternate in turn. The game is lost by the one who is forced to write a number greater than . Assuming perfect play, who will win the game.