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

//INSERT ABOVE HERE
signed main(){
  Int h,w;
  cin>>h>>w;
  vector<string> s(h);
  for(Int i=0;i<h;i++) cin>>s[i];
  
  auto check=
    [&](Int a,Int b){
      if(!a&&!b) return;
      auto in=[&](Int y,Int x){return 0<=y&&y<h&&0<=x&&x<w;};
      Int used[100][100];
      memset(used,0,sizeof(used));
      for(Int i=0;i<h;i++){
	for(Int j=0;j<w;j++){
	  if(used[i][j]||s[i][j]!='#') continue;	  
	  Int cnt=0;
	  while(in(i+cnt*a,j+cnt*b)&&s[i][j]==s[i+cnt*a][j+cnt*b]){
	    used[i+cnt*a][j+cnt*b]=1;
	    cnt++;
	  }
	  if(cnt&1) return;
	}
      }
      cout<<"YES"<<endl;
      exit(0);
    };
  
  for(Int a=-h;a<=h;a++)
    for(Int b=-w;b<=w;b++)
      check(a,b);
  
  cout<<"NO"<<endl;
  return 0;
}