Score : 1700 points
We have a grid with N rows and N columns. The cell at the i-th row and j-th column is denoted (i, j).
Initially, M of the cells are painted black, and all other cells are white. Specifically, the cells (a_1, b_1), (a_2, b_2), ..., (a_M, b_M) are painted black.
Snuke will try to paint as many white cells black as possible, according to the following rule:
Find the number of black cells when no more white cells can be painted black.
The input is given from Standard Input in the following format:
N M a_1 b_1 a_2 b_2 : a_M b_M
Print the number of black cells when no more white cells can be painted black.
3 2 1 2 2 3
3
It is possible to paint one white cell black, as follows:
2 2 1 1 1 2
4
It is possible to paint two white cells black, as follows:
4 3 1 2 1 3 4 4
3
No white cells can be painted black.