/* To determine whether the matrix is a triangular matrix.

First, you will be given N, which is the size of the matrix.

Then you will be given N rows of integers, where each row consists of

N integers separated by spaces.

If the input matrix is triangular, then print yes. Otherwise, print

no. */

#include <stdio.h>

#include <stdlib.h>

int main()

{

int a[10][10],n,i,j,flag=0;

scanf("%d",&n);

for(i=0;i<n;i++)

{

for(j=0;j<n;j++)

{scanf("%d",&a[i][j]);

}

}

for(i=0;i<n;i++)

{

for(j=0;j<n;j++)

{

if(!(i==j) &&(i>j || j>i) ) flag=1;

}

}

if(!(flag))printf("no\n");

else printf("yes");

return 0;

}