#include <bits/stdc++.h>
using namespace std;
const int N = 2010;
int n, m;
string s[N];
int cnt[N];
int now[N];
bool flag = 1;
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) {
    cin >> s[i];
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (s[i][j] == '1') cnt[j]++;
    }
  }
  for (int i = 0; i < n; i++) {
    flag = 1;
    for (int j = 0; j < m; j++) {
      now[j] = cnt[j] - (s[i][j] - '0');
      if (!now[j]) flag = 0;
    }
    if (flag) break;
  }
  if (flag)
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
