#include <bits/stdc++.h>
 
#define rep(i, n)      for (int i = 0; i < (n); i++)
#define repr(i, n)     for (int i = (n) - 1; i >= 0; i--)
#define repe(i, l, r)  for (int i = (l); i < (r); i++)
#define reper(i, l, r) for (int i = (r) - 1; i >= (l); i--)
#define repi(i, l, r)  for (int i = (l); i <= (r); i++)
#define repir(i, l, r) for (int i = (r); i >= (l); i--)
#define range(a) a.begin(), a.end()
void init_io() { std::cin.tie(nullptr); std::ios::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(15); }
 
using namespace std;
using ll = long long;

int main() { init_io();
  int H, W; cin >> H >> W;
  vector<string> G(H);
  rep(i, H) cin >> G[i];
  vector<int> col(W), row(H);
  rep(i, H) rep(j, W) {
    col[j] += G[i][j] - '0';
    row[i] += G[i][j] - '0';
  }
  bool any = false;
  rep(i, H) rep(j, W) {
    any |= row[i] == 0 && col[j] == 0;
    any |= row[i] == W && col[j] == H;
  }
  cout << (!any ? "YES" : "NO") << endl;
}