eolymp
bolt
Try our new interface for solving problems
Problems

Number of hanging vertices 1

Number of hanging vertices 1

Time limit 3 seconds
Memory limit 128 MiB

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

Input data

The first line contains number n~(1 \le n \le 1000). The next n lines contain the adjacency matrix.

Output data

Print the number of hanging vertices in a graph.

Examples

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