#include <bits/stdc++.h>
const int maxn = 2007;
int map[maxn][maxn], sum[maxn], n, m;
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) {
      scanf("%1d", map[i] + j);
      sum[j] += map[i][j];
    }
  for (int i = 1, j; i <= n; i++) {
    for (j = 1; j <= m; j++)
      if (sum[j] - map[i][j] == 0) break;
    if (j > m) return 0 * puts("YES");
  }
  return 0 * puts("NO");
}
