#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int H,W; cin >> H >> W;
    vector<int> X(H),Y(W);
    for(int i=0; i<H; i++){
        string s; cin >> s;
        for(int k=0; k<W; k++) if(s.at(k) == '1') X.at(i)++,Y.at(k)++;
    }
    int ng1 = 0,ng2 = 0;
    for(auto x : X) if(x == 0 || x == W) ng1++;
    for(auto x : Y) if(x == 0 || x == H) ng2++;
    if(ng1 && ng2) cout << "NO\n";
    else cout << "YES\n";
}