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Depth First Search - Labyrinths

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 × 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 (1n, m100). 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.

Time limit 1 second
Memory limit 128 MiB
Input example #1
5 4
0 0 1 0
0 1 0 0
1 1 1 1
0 0 0 0
1 1 0 0
Output example #1
3
Input example #2
3 3
0 0 0
0 1 0
0 0 0
Output example #2
1
Source 2009 SCS Group D, Day 9, 10