#include "bits/stdc++.h"
#include<vector>
#include<iostream>
#include<queue>
#include<algorithm>
#include<map>
#include<set>
#include<iomanip>
#include<assert.h>
#include<unordered_map>
#include<unordered_set>
#include<string>
#include<stack>
#include<complex>
#pragma warning(disable:4996)
using namespace std;
using ld = long double;
template<class T>
using Table = vector<vector<T>>;
const ld eps=1e-9;

#define WHATS(var)cout<<__LINE__<<' '<<#var<<"="<<var<<endl;

template<class S, class T> ostream& operator <<(ostream &os, const pair<S, T> v){
os << "( " << v.first << ", " << v.second << ")"; return os;
}
template<class T> ostream& operator <<(ostream &os, const vector<T> &v){
for(int i = 0; i < v.size(); i++){if(i > 0){os << " ";} os << v[i];} return os;
}
template<class T> ostream& operator <<(ostream &os, const vector<vector<T>> &v){
for(int i = 0; i < v.size(); i++){if(i > 0){os << endl;} os << v[i];} return os;
}
template<class T> ostream& operator <<(ostream &os, const vector<set<T>> &v){
for(int i = 0; i < v.size(); i++){if(i > 0){os << endl;} os << v[i];} return os;
}
template<class T> ostream& operator <<(ostream &os, const set<T> &v){
int i=0;
for(auto it:v){
	if(i > 0){os << ' ';}
	os << it;
	i++;
} 
return os;
}
/*
1 2 3 4 5 6 7 8 9 10 11 12 13 14

12 1 11
13 3 10
14 5 9
15 7 8
16 2 14
17 4 13
18 6 12

1-12

11 1 10
12 3 9
13 5 8
13 6 7
14 2 12
15 4 11
*/

const int MAX_X=2220;

using ll=long long ;
int H,W;
vector<vector<int>>field;
vector<vector<int>>sums;
int main() {
	ios::sync_with_stdio(false);
	int H,W;cin>>H>>W;
	field=vector<vector<int>>(H,vector<int>(W));
	sums=vector<vector<int>>(H+1,vector<int>(W+1));
	for(int y=0;y<H;++y){
		string st;cin>>st;
		for(int x=0;x<W;++x){
			field[y][x]=st[x]=='1';
			sums[y+1][x+1]=sums[y][x+1]+sums[y+1][x]-sums[y][x]+field[y][x];
		}
	}
	vector<vector<int>>oks(H,vector<int>(W));
	oks[0][0]=true;
	bool ok=false;
	for(int y=0;y<H;++y){
		for(int x=0;x<W;++x){
			if(oks[y][x]){
				{
					int xline=sums[y+1][W]-sums[y][W]-sums[y+1][x]+sums[y][x];
					if(xline==0||xline==W-x){
					}else{
						if(y==H-1)ok=true;
						else oks[y+1][x]=true;

					}
					int yline=sums[H][x+1]-sums[H][x]-sums[y][x+1]-sums[y][x];
					if(yline==0||yline==H-y){

					}else{
						if(x==W-1)ok=true;
						else oks[y][x+1]=true;
					}
				}
			}
		}
	}
	if(ok)cout<<"YES"<<endl;
	else cout<<"NO"<<endl;
	return 0;
}