Vote manipulation
Source: Mexico National Olympiad 2017, Problem 6
November 7, 2017
combinatorics
Problem Statement
Let and be positive integers. ballot boxes are placed in a line. Two players and play by turns, beginning with , in the following manner. Each turn, chooses two boxes and places a ballot in each of them. Afterwards, chooses one of the boxes, and removes every ballot from it. wins if after some turn of , there exists a box containing ballots. For each , find the minimum value of such that can guarantee a win independently of how plays.