Description

Given edges of a graph with N nodes. Check whether it is a tree.

Input Format

First line: one positive integers N (N <= 100).
Next N lines: an N*N 0/1 matrix A={a[i][j]}, indicating whether there exists an edge between node i and node j (a[i][j]=1) or not (a[i][j]=0).

Output Format

One integer, 1 if the graph is a tree, or 0 otherwise.

4
0 1 0 1
1 0 1 0
0 1 0 0
1 0 0 0

1