MathDB
Almost completely different scores on IMO day 1

Source: ITAMO 2016, Problem 2

May 11, 2016
combinatorics

Problem Statement

A mathematical contest had 33 problems, each of which was given a score between 00 and 77 (00 and 77 included). It is known that, for any two contestants, there exists at most one problem in which they have obtained the same score (for example, there are no two contestants whose ordered scores are 7,1,27,1,2 and 7,1,57,1,5, but there might be two contestants whose ordered scores are 7,1,27,1,2 and 7,2,17,2,1). Find the maximum number of contestants.