#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7, maxN = 2e3 + 6, maxV = 6561 + 5;
int n, m, sm[maxN];
string mat[maxN];
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    cin >> mat[i];
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      sm[j] += mat[i][j] - '0';
    }
  }
  for (int i = 0; i < n; i++) {
    bool can = true;
    for (int j = 0; j < m; j++) {
      sm[j] -= mat[i][j] - '0';
      if (sm[j] == 0) can = false;
      sm[j] += mat[i][j] - '0';
    }
    if (can) {
      cout << "YES\n";
      return 0;
    }
  }
  cout << "NO\n";
}
