#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;

#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007; // 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};

struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
    cerr << fixed << setprecision(10);
  }
} iosetup;
/*-------------------------------------------------*/
int main() {
  int h, w; cin >> h >> w;
  vector<vector<int> > a(h, vector<int>(w));
  REP(i, h) REP(j, w) {
    char c; cin >> c;
    a[i][j] = c - '0';
  }
  bool exist = false;
  REP(i, h) {
    if (count(ALL(a[i]), 1) == 0) exist = true;
  }
  if (exist) {
    REP(j, w) {
      int cnt = 0;
      REP(i, h) {
        if (a[i][j] == 1) ++cnt;
      }
      if (cnt == 0) {
        cout << "NO\n";
        return 0;
      }
    }
  }
  exist = false;
  REP(i, h) {
    if (count(ALL(a[i]), 0) == 0) exist = true;
  }
  if (exist) {
    REP(j, w) {
      int cnt = 0;
      REP(i, h) {
        if (a[i][j] == 0) ++cnt;
      }
      if (cnt == 0) {
        cout << "NO\n";
        return 0;
      }
    }
  }
  cout << "YES\n";
  return 0;
}