题目描述

The Do-Barareh military area is like an $n\times m$ grid, each cell of which has a specific height. The commander of this military area is looking for a rectangular sub-area of this area, with width and height least $2$, whose its four corner cells are higher than the rest of its cells. He plans to install watchtowers in the corners of this sub-area to monitor the entire sub-area and use it for ammunition storage. Your job is to help the commander to find out how many valid sub-areas there are to choose as the ammunition storage. You can assume cell heights are distinct.

输入格式

The first line of input contains two space-separated integers $n$ and $m$ ($2 \leqslant n,m \leqslant 750$). Each of the next $n$ lines contains $m$ space-separated integers showing the cell heights. It is guaranteed cell heights are distinct numbers between $1$ and $nm$ (inclusive).

输出格式

Print the number of valid sub-areas to be used as an ammunition storage.

3 3
9 4 8
2 1 3
7 5 6

7