Shading a Square Grid
Source: 2nd Final Mathematical Cup Junior Division P3 (2020)
October 1, 2020
combinatoricssquare grid
Problem Statement
Let , be positive integers, , and a grid of unit squares is
given. Ana and Maya take turns in coloring the grid in the following way: in each turn, a unit square is colored black in such a way that no two black cells have a common side or vertex. Find the smallest positive integer , such that they can obtain a configuration in which each row and column contains exactly black cells. Draw one example.