#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  int h, w;
  cin >> h >> w;
  string str[h];
  for (int i = 0; i < h; i++) {
    cin >> str[i];
  }
  int cnt = 0;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      cnt += (str[i][j] == '#');
    }
  }
  if (cnt%2 || cnt == 0) {
    std::cout << "NO" << std::endl;
    return 0;
  }

  bool ok = false;
  int x, y;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (str[i][j] == '#') {
	x = j;
	y = i;
	ok = true;
      }
      if (ok) break;
    }
    if (ok) break;
  }

  for (int i = -h; i < h; i++) {
    for (int j = -w; j < w; j++) {
      bool vis[h][w];
      memset(vis, false, sizeof(vis));
      int tcnt = 0;
      for (int k = 0; k < h; k++) {
	for (int l = 0; l < w; l++) {
	  if (str[k][l] != '#' || vis[k][l]) {
	    continue;
	  }
	  if (k+i >= 0 && l+j >= 0 && k+i < h && l+j < w && str[k+i][l+j] == '#' &&
	      !vis[k+i][l+j]) {
	    tcnt++;
	    vis[k][l] = true;
	    vis[k+i][l+j] = true;
	  }
	}
      }
      if (tcnt*2 == cnt) {
	std::cout << "YES" << std::endl;
	return 0;
      }
    }
  }

  std::cout << "NO" << std::endl;
  return 0;
}