1 #include<iostream>
 2 #include<string>
 3 #include<cstdio>
 4 #include<vector>
 5 #include<queue>
 6 #include<stack>
 7 #include<set>
 8 #include<algorithm>
 9 #include<cstring>
10 #include<stdlib.h>
11 #include<math.h>
12 using namespace std;
13 #define ll __int64
14 string a[51];
15 int n,m;
16 int can(int x,int y){
17     if(x<n-1&&y<m-1&&a[x][y]==‘0‘&&a[x][y+1]==‘0‘&&a[x+1][y]==‘0‘&&a[x+1][y+1]==‘0‘) return 1;
18     else return 0;
19 }
20 void Go(int x,int y){
21     a[x][y]=a[x][y+1]=a[x+1][y]=a[x+1][y+1]=‘1‘;
22 }
23 void Back(int x,int y){
24     a[x][y]=a[x][y+1]=a[x+1][y]=a[x+1][y+1]=‘0‘;
25 }
26 int dfs(){
27     for(int i=0;i<n;i++)
28        for(int j=0;j<m;j++)
29        if(can(i,j)){
30             Go(i,j);
31             if(!dfs()){
32                 Back(i,j);
33                 return 1;
34             }
35             Back(i,j);
36        }
37        return 0;
38 }
39 int main(){
40     while(cin>>n>>m){
41         for(int i=0;i<n;i++) cin>>a[i];
42         if(dfs()) cout<<"Yes"<<endl;
43         else cout<<"No"<<endl;
44     }
45 }