From adjacency matrix to edge list

A simple undirected graph is defined by an adjacency matrix.

Output its representation as a list of edges.

Input

The first line of the input file contains the number N (1 ≤ N ≤ 100). Then there are N lines with N elements in each - a description of the adjacency matrix.

Output

In the output file, output a list of edges, ordered first by the first vertex in the pair of vertices that describes the edge, and then by the second.

Examples