IMO Shortlist 1998 problem C6
Avg:
Avg:
Ten points are marked in the plane so that no three of them lie on a line. Each pair of points is connected with a segment. Each of these segments is painted with one of
colors, in such a way that for any
of the ten points, there are
segments each joining two of them and no two being painted with the same color. Determine all integers
,
, for which this is possible.





Izvor: Međunarodna matematička olimpijada, shortlist 1998