The digits 0,1,2,...,9 are written in a 10x10 table , each number appearing 10 times .
(a) Is it possible to write them in such a way that in any row or column there would be not more than 4 different digits?
(b) Prove that there must be a row or column containing more than 3 different digits .{ L . D . Kurlyandchik , Leningrad) combinatoricsDigitssquare table