MathDB
2012-2013 Winter OMO #43

Source:

January 16, 2013
Online Math Openpigeonhole principleblogs

Problem Statement

In a tennis tournament, each competitor plays against every other competitor, and there are no draws. Call a group of four tennis players ``ordered'' if there is a clear winner and a clear loser (i.e., one person who beat the other three, and one person who lost to the other three.) Find the smallest integer nn for which any tennis tournament with nn people has a group of four tennis players that is ordered.
Ray Li