#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600
#define long long long // for codeforces

bool solve(){
  int h,w;
  cin>>h>>w;
  vector<string> vec(h);
  rep(i,h) cin>>vec[i];

  int cnt=0;
  rep(i,h)rep(j,w) if(vec[i][j]=='#') cnt++;
  if(cnt==0) return false;
  if(cnt%2==1) return false;

  auto isok = [&](int dx, int dy){
    vector<vector<bool>> checked(h,vector<bool>(w,false));
    rep(i,h)rep(j,w) if(vec[i][j]=='#' && checked[i][j]==false){
      int nx = i+dx, ny = j+dy;
      if(nx>=h || ny>=w) return false;
      if(vec[nx][ny]=='.') return false;
      checked[nx][ny] = true;
    }//dbg(mp(dx,dy));
    return true;
  };

  for(int i=-h; i<h; h++) for(int j=-w; j<w; j++) if(!(i==0 && j==0)){
    if(isok(i,j)) return true;
  }

  return false;
}

int main(){
  if(solve()) cout<<"YES"<<endl;
  else cout<<"NO"<<endl;

  return 0;
}