Graph on a Table

You are given a table with $N$ rows and $M$ columns. Let's denote the cell in row $r$ and column $c$ by $(r, c)$. You are also given $Q$ rectangles in this table. Consider a directed acyclic graph such that each vertex corresponds to a cell of the table (so there are $N \cdot M$ vertices) and there is an edge from cell $(r_1, c_1)$ to cell $(r_2, c_2)$ if and only if: - $r_1 < r_2, c_1 < c_2$ - t