#include <bits/stdc++.h>
using namespace std;
const int maxnum = 2005;
char str[maxnum][maxnum];
int state[maxnum];
int main() {
  int m, n;
  while (~scanf("%d%d", &n, &m)) {
    memset(state, 0, sizeof(state));
    for (int i = 0; i < n; ++i) {
      scanf("%s", str[i]);
      for (int j = 0; j < m; ++j) {
        if (str[i][j] == '1') state[j] += '1';
      }
    }
    bool ans = false;
    for (int i = 0; i < n; ++i) {
      bool judge = true;
      for (int j = 0; j < m; ++j) {
        if (judge == false) break;
        if (str[i][j] == '1') {
          judge = state[j] - '1';
        }
        if (str[i][j] == '0') {
          judge = state[j];
        }
      }
      if (judge) {
        ans = true;
        break;
      }
    }
    if (ans)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
