#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i, j, l, p;
  cin >> n >> m;
  p = n;
  int arr[m];
  string s[n];
  int k = 0;
  for (i = 0; i < m; i++) {
    arr[i] = 0;
  }
  while (p-- > 0) {
    cin >> s[k];
    for (i = 0; i < m; i++) {
      arr[i] = arr[i] + (s[k][i] % 48);
    }
    k++;
  }
  for (i = 0; i < n; i++) {
    for (j = 0; j < m; j++) {
      arr[j] -= (s[i][j] % 48);
    }
    for (l = 0; l < m; l++) {
      if (arr[l] == 0) break;
    }
    if (l == m) {
      cout << "YES" << endl;
      return 0;
    }
    for (j = 0; j < m; j++) {
      arr[j] += (s[i][j] % 48);
    }
  }
  cout << "NO";
  return 0;
}
