IMO Shortlist 1986 problem 9


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2. travnja 2012.
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Given a finite set of points in the plane, each with integer coordinates, is it always possible to color the points red or white so that for any straight line L parallel to one of the coordinate axes the difference (in absolute value) between the numbers of white and red points on L is not greater than 1?
Izvor: Međunarodna matematička olimpijada, shortlist 1986