10th ibmo - chile 1995/q4.
Source: Spanish Communities
May 7, 2006
ceiling functionsymmetrycombinatorics unsolvedcombinatorics
Problem Statement
In a grid are there are token. Every token dominates every square on its same row (), its same column (), and diagonal ()(Note that the token does not \emph{dominate} the diagonal (), determine the lowest number of tokens that must be on the board to dominate all the squares on the board.