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1998 segments, some intersect, show existence of points

Source: Ukraine 1998 Grade 10 P3

June 5, 2021
geometrycombinatoricscombinatorial geometry

Problem Statement

A finite set of segments on a line has the following property: In any subset of 19981998 segments there are two having a common point. Show that there exist 19971997 points on the line such that each segment contains at least one of these points.