#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<ll, ll>;
const ll MOD = 1e9 + 7, N = 2e3 + 10;
ll a[N][N];
ll sum[N];
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  ll n, m;
  cin >> n >> m;
  string s[n];
  for (ll i = 0; i < n; i++) {
    cin >> s[i];
    for (ll j = 0; j < m; j++) {
      a[i][j] = (s[i][j] - '0');
      sum[j] += a[i][j];
    }
  }
  for (ll i = 0; i < n; i++) {
    ll chk = 1;
    for (ll j = 0; j < m; j++) {
      sum[j] -= a[i][j];
      if (!sum[j]) chk = 0;
    }
    if (chk) {
      cout << "YES\n";
      return 0;
    }
    for (ll j = 0; j < m; j++) {
      sum[j] += a[i][j];
    }
  }
  cout << "NO\n";
  return 0;
}
