View Code of Problem 441

#include <stdio.h>
main(){
	int n,m;
	scanf("%d%d",&n,&m);
	while(n&&m){
		int i,j,a[n][m],t=1;
		for(i=0;i<n;i++)
			for(j=0;j<m;j++)
				scanf("%d",&a[i][j]);
		for(i=0;i<n;i++)
			for(j=0;j<m;j++){
				if((i+j)%2==0)if(a[i][j]!=a[0][0]){
					t=0;break;
				}
				if((i+j)%2!=0)if(a[i][j]!=a[0][1]){
					t=0;break;
				}
			}
		if(t&&a[0][0]!=a[0][1])printf("Yes\n");
			else printf("No\n");
		scanf("%d%d",&n,&m);
	}
}