Given a directed graph, output YES if it is acyclic, and NO otherwise.

Input Specification

~N \le 1\,000~, the number of vertices.
An adjacency matrix, ~N~ rows with ~N~ numbers (0 or 1).

Output Specification

YES or NO.

Sample Input 1

3
0 1 0
0 0 1
1 0 0

Sample Output 1

NO

Sample Input 2

3
0 1 0
0 0 1
0 0 0

Sample Output 2

YES