#include <iostream>
#include <vector>
#include <set>
#include <map>
using namespace std;
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){
    cout << "NO" << endl;
    return 0;
  }
  int C = 0;
  set<pair<int,int>> X[2*h*w];
  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;
          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});
          }
        }
      }
    }
  }
  for(int i = 0; 2*h*w > i; i++){
    if(X[i].size() == c){
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
}