Placing stones on a 1999 x 1999 board
Source: Japanese MO Finals 1999
February 11, 2011
floor functionrotationceiling functioncombinatorics proposedcombinatorics
Problem Statement
One can place a stone on each of the squares of a board. Find the minimum number of stones that must be placed so that, for any blank square on the board, the total number of stones placed in the corresponding row and column is at least .