#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
using namespace std;
struct d{
  int a,b,c;
  bool operator<(d x){
    if(a == x.a){
      if(b == x.b){
        return c < x.c;
      }
      return b < x.b;
    }
    return a < x.a;
  }
  bool operator==(d x){
    return a==x.a && b==x.b && c==x.c;
  }
  bool operator>(d x){
    return !((*this) < x || (*this) == x);
  }
};
int main(){
  int h,w;cin>>h>>w;
  vector<vector<char>> A(h,vector<char>(w));
  int c = 0;
  for(int i = 0; h > i; i++){
    for(int j = 0; w > j; j++){
      cin>>A[i][j];
      if(A[i][j] == '#')c++;
    }
  }
  if(c%2 || c==0){
    cout << "NO" << endl;
    return 0;
  }
  int C = 0;
  set<pair<int,int>> X[h*w];
  vector<d> ZZ;
  for(int i = 0; h > i; i++){
    for(int j = 0; w > j; j++){
      for(int k = i; h > k; k++){
        for(int l = j; w > l; l++){
          //cout << (i-k)*w+(j-l)+h*w << endl;
          int tmp = (i-k)*w+(j-l)+h*w;
          ZZ.push_back({tmp,(i-k),(j-l)});
          if(i==k && j==l)continue;
          if(A[i][j] == '#' && A[k][l] == '#'){
            //cout << i-k << " " << j-l << endl;
            X[(i-k)*w+(j-l)+h*w].insert({i,j});
            X[(i-k)*w+(j-l)+h*w].insert({k,l});
          }
        }
      }
    }
  }
  //sort(ZZ.begin(),ZZ.end());
  //ZZ.erase(unique(ZZ.begin(),ZZ.end()),ZZ.end());
  //for(int i = 0; ZZ.size() > i; i++){
  //  cout << ZZ[i].a << " " << ZZ[i].b << " " << ZZ[i].c << endl;
  //}
  for(int i = 0; h*w > i; i++){
    if(X[i].size() == c){
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
}