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50 points in plane

Source: JBMO 2007, Bulgaria, problem 3

June 28, 2007
combinatorics proposedcombinatoricscombinatorial geometryHi

Problem Statement

Given are 5050 points in the plane, no three of them belonging to a same line. Each of these points is colored using one of four given colors. Prove that there is a color and at least 130130 scalene triangles with vertices of that color.