# Checking for an undirected graph

Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

For a given square matrix n x n of zeros and ones determine whether it can be the adjacency matrix of a simple undirected graph. The simple graph does not contain loops and multiple edges.

## Input

The first line contains the value of n (1 ≤ n ≤ 100). Each of the next n lines contains n numbers, describing the adjacency matrix.

## Output

Print YES, if the graph is simple undirected and NO otherwise.

## Examples

Input #1

Answer #1

Input #2

Answer #2

Submissions 13K

Acceptance rate 40%