MathDB
Vote manipulation

Source: Mexico National Olympiad 2017, Problem 6

November 7, 2017
combinatorics

Problem Statement

Let n2n \geq 2 and mm be positive integers. mm ballot boxes are placed in a line. Two players AA and BB play by turns, beginning with AA, in the following manner. Each turn, AA chooses two boxes and places a ballot in each of them. Afterwards, BB chooses one of the boxes, and removes every ballot from it. AA wins if after some turn of BB, there exists a box containing nn ballots. For each nn, find the minimum value of mm such that AA can guarantee a win independently of how BB plays.