Itamo 2015, problem 6, hard combinatorics
Source: Itamo 2015
May 30, 2015
combinatoricsGame Theory
Problem Statement
Ada and Charles play the following game:at the beginning, an integer n>1 is written on the blackboard.In turn, Ada and Charles remove the number k that they find on the blackboard.In turn Ad and Charles remove the number k that they find on the blackboard and they replace it :
1 -either with a positive divisor k different from 1 and k
2- or with k+1
At the beginning each players have a thousand points each.When a player choses move 1, he/she gains one point;when a player choses move 2, he/she loses one point.The game ends when one of the tho players is left with zero points and this player loses the game.Ada moves first.For what values Chares has a winning strategy?