MathDB
Points and colored segments

Source: All-Russian 2021/9.1

April 19, 2021
combinatoricsAll Russian OlympiadRussia

Problem Statement

On a circle there're 10001000 marked points, each colored in one of kk colors. It's known that among any 55 pairwise intersecting segments, endpoints of which are 1010 distinct marked points, there're at least 33 segments, each of which has its endpoints colored in different colors. Determine the smallest possible value of kk for which it's possible.