#include <bits/stdc++.h>
using namespace std;
int N, M;
int sum[2003];
string av[2003];
void readin() {
  cin >> N >> M;
  for (int i = 0; i < N; ++i) {
    cin >> av[i];
  }
}
bool check(int i) {
  for (int j = 0; j < M; ++j) {
    if (sum[j] - (av[i][j] - '0') == 0) {
      return false;
    }
  }
  return true;
}
void process() {
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < M; ++j) {
      sum[j] += av[i][j] - '0';
    }
  }
  for (int i = 0; i < N; ++i) {
    if (check(i)) {
      cout << "YES" << endl;
      return;
    }
  }
  cout << "NO" << endl;
  return;
}
int main() {
  readin();
  process();
  return 0;
}
