Chef and Spice Grid

You have an $N \times M$ grid consisting of $N$ rows numbered $1$ to $N$ from top to bottom and $M$ columns numbered $1$ to $M$ from left to right. Each cell of the grid is initially white. You can perform the following operation any number of times (possibly zero): - Select a row $i$ $(1 \le i \le N)$ and paint all the cells in row $i$ black. - Or select a column $i$ $(1 \le i \le M)$ and paint