Square punch

During the Summer School August 2009 the hole punch was tested that makes the square holes. The size of the badge is $n\cdot m$ cells, each of which can be punched. On the diagram $1$ is a punched cell, $0$ is not punched. How many little badges will remain after using a punch?

Input

The first line contains the sizes of the badge $n$ and $m(1\le n,m\le 100)$. The next $n$ lines contain a diagram of the punctured badge.

Output

Print the number of little badges that will remain after using a punch.

Examples