#include <bits/stdc++.h>
using namespace std;
int n, m, tot[2005], cnt[2005][2005];
bool chk(int x) {
  for (int i = 1; i <= m; i++)
    if (tot[i] - cnt[x][i] <= 0) return false;
  return true;
}
int main() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) {
      scanf("%1d", &cnt[i][j]);
      tot[j] += cnt[i][j];
    }
  for (int i = 1; i <= n; i++)
    if (chk(i)) {
      printf("YES\n");
      return 0;
    }
  printf("NO\n");
  return 0;
}
