poj2864

//poj2864 简单题
#include <iostream>
using namespace std;

int main()
{
	int n, d;
	cin>>n>>d;
	int a[505][105];
	while(n && d)
	{
		for(int i = 0; i < d; i++)
		{
			for(int j = 0; j < n; j++)
			{
				cin>>a[i][j];
			}
		}
		bool ok = true;
		for(int i = 0; i < n; i++)
		{
			ok = true;
			for(int j = 0; j < d; j++)
				if(!a[j][i])
					ok = false;
			if(ok)
				break;
		}
		if(ok)
	 		cout<<"yes"<<endl;
		else
			cout<<"no"<<endl;
		cin>>n>>d;
	}
	return 0;
}