1 #include <iostream>
2 #define MAXN 600
3 using namespace std;
4
5 int _m[MAXN][MAXN];
6
7 int main()
8 {
9 //freopen("acm.acm","r",stdin);
10 int c;
11 int r;
12 int i;
13 int j;
14 int sum;
15
16 while(cin>>c>>r,c||r)
17 {
18
19 for(i = 0; i < r; ++ i)
20 {
21 for(j = 0; j < c; ++ j)
22 {
23 cin>>_m[i][j];
24 }
25 }
26
27 for(j = 0; j < c; ++ j)
28 {
29 sum = 0;
30 for(i = 0; i < r; ++ i)
31 {
32 //sum += _m[i][j];
33 if(_m[i][j] == 0)
34 {
35 break;
36 }
37 }
38 if(i == r)
39 {
40 cout<<"yes"<<endl;
41 break;
42 }
43 }
44 if(j == c)
45 {
46 cout<<"no"<<endl;
47 }
48 }
49
50 }
