KöMaL 2011 B4403
There are chessmen standing on some fields of a 20×20 chessboard. The rule is that a chessman can be removed from the board if at least a half of the fields is vacant in its row or in its column. What is the maximum possible number of chessmen on the board if all of them can be removed in a sequence of such steps?
Official text KöMaL. Quoted with source.
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