#include <bits/stdc++.h>
using namespace std;
int i, j, n, m, a, ck = 0, ck2 = 1;
char in[2050][2050];
map<int, int> x;
int main() {
  scanf("%d %d", &m, &n);
  for (i = 1; i <= m; i++) {
    scanf("%s", in[i]);
    for (j = 0; j < n; j++) {
      if (in[i][j] - 48 == 1) {
        x[j]++;
      }
    }
  }
  for (i = 1; i <= m; i++) {
    for (j = 0; j <= n; j++) {
      if (in[i][j] - 48 == 1) {
        if (x[j] == 1) ck2 = 0;
      }
    }
    if (ck2 == 1) {
      ck = 1;
      break;
    } else {
      ck2 = 1;
    }
  }
  if (ck == 1)
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
