The cells of the $200 \times 200$ table are painted black and white so that there are $404$ more black cells than white ones. Prove that there is a $2 \times 2$ square in which the number of white cells is odd.
Source:
Tags: combinatorics, Coloring
The cells of the $200 \times 200$ table are painted black and white so that there are $404$ more black cells than white ones. Prove that there is a $2 \times 2$ square in which the number of white cells is odd.