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Graph representation

Number of hanging vertices 1

Given a simple undirected unweighted graph. Count the number of hanging vertices in it. The vertex is hanging, if its degree is 1.

Input

The first line contains number n (1n1000). The next n lines contain the adjacency matrix.

Output

Print the number of hanging vertices in a graph.

prb5080.gif

Time limit 3 second
Memory limit 128 MiB
Input example #1
2
0 1
1 0
Output example #1
2
Input example #2
3
0 1 1
1 0 1
1 1 0
Output example #2
0