#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e9 + 9;
const long long N = 3e5 + 5;
long long t[N * 4];
vector<long long> lz[4 * N];
long long A[N], f[N], n, k;
string s[N];
void solve() {
  long long i, j, x = 0, y = 0, a = 0, b, ans = 0;
  cin >> n >> k;
  for (i = 0; i < n; i++) cin >> s[i];
  for (i = 0; i < n; i++)
    for (j = 0; j < k; j++) A[j] += (s[i][j] - '0');
  for (i = 0; i < n; i++) {
    for (j = 0; j < k; j++) A[j] -= (s[i][j] - '0');
    if ((*min_element(A, A + k)) > 0) {
      cout << "YES";
      return;
    }
    for (j = 0; j < k; j++) A[j] += (s[i][j] - '0');
  }
  cout << "NO";
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t = 1, i;
  while (t--) {
    solve();
  }
}
