#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

bool solve(vector<string> bd) {
  int h = bd.size(), w = bd[0].size();

  int target = 0;
  REP (i, h) REP (j, w) target += bd[i][j] == '#';
  
  if (!target)
    return false;

  for (int y = 0; y < h; y++) {
    for (int x = 1-w; x < w; x++) {
      if (!x && !y) continue;
      vector<string> tmp = bd;
      int cnt = 0;
      REP (i, h) REP (j, w) {
        if (tmp[i][j] != '#') continue;
        if (i+y < h && j+x >= 0 && j+x < w && tmp[i+y][j+x] == '#') {
          tmp[i][j] = tmp[i+y][j+x] = '.';
          cnt += 2;
        }
      }
      if (cnt == target)
        return true;
    }
  }
  return false;  
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int h, w;
  cin >> h >> w;

  vector<string> bd(h);
  REP (i, h) cin >> bd[i];

  if (solve(bd))
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  
  return 0;
}