/* -*- coding: utf-8 -*-
 *
 * 179.cc: No.179 塗り分け - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_H = 50;
const int MAX_W = 50;

/* typedef */

/* global variables */

bool flds[MAX_H][MAX_W], used[MAX_H][MAX_W];

/* subroutines */

/* main */

int main() {
  int h, w;
  cin >> h >> w;

  int hw = h * w, bn = 0;

  for (int y = 0; y < h; y++) {
    string s;
    cin >> s;
    for (int x = 0; x < w; x++) {
      if (s[x] == '#') flds[y][x] = true, bn++;
      else flds[y][x] = false;
    }
  }

  if (bn == 0 || (bn & 1) != 0) {
    puts("NO");
    return 0;
  }

  for (int dy = 0; dy < h; dy++)
    for (int dx = -(w - 1); dx < w; dx++) {
      if (dx == 0 && dy == 0) continue;
      memset(used, false, sizeof(used));

      bool ok = true;
      for (int y = 0; ok && y < h; y++)
	for (int x = 0; ok && x < w; x++)
	  if (flds[y][x] && ! used[y][x]) {
	    used[y][x] = true;
	    int x0 = x + dx, y0 = y + dy;
	    if (x0 >= 0 && x0 < w && y0 < h && flds[y0][x0])
	      used[y0][x0] = true;
	    else
	      ok = false;
	  }

      if (ok) {
	puts("YES");
	return 0;
      }
    }

  puts("NO");
  return 0;
}