#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
 
using namespace std;
 
#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(long long i=(a);i<(b);++i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
 
#define MOD 1000000007

int d[1000][1000];

int main(){
  int h,w;
  cin >> h >> w;
  vector<string> v;
  rep(i,0,h){
    string s;
    cin>>s;
    v.pb(s);
  }
  rep(y,0,h){
    rep(x,0,w){
      if(x==0&&y==0)continue;
      clr(d,0);
      rep(y1,0,h){
        rep(x1,0,w){
          if(y1+y>h)continue;
          if(x1+x>w)continue;
          if(v[y1][x1]=='#'&&d[y1][x1]==0&&v[y1+y][x1+x]=='#'&&d[y1+y][x1+x]==0){
            //d[y1][x1] = 1;
            //d[y1+y][x1+x] = 1;
          }
        }
      }
      int flag = 1;
      rep(y1,0,h){
        rep(x1,0,w){
          if(v[y1][x1]=='#'&&d[y1][x1]==0){
            flag = 0;
          }
        }
      }
      if(flag == 1){
        cout << "YES" << endl;
        return 0;
      }
    }
  }
  cout << "NO" << endl;
  return 0;
}