#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) {
    std::cout << "NO" << std::endl;
    return 0;
  }

  bool memo[2*h+1][2*w+1];
  memset(memo, false, sizeof(memo));
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      bool goout = false;
      if (str[i][j] == '#') {
	for (int k = 0; k < h; k++) {
	  for (int l = 0; l < w; l++) {
	    if (i == k && j == l) continue;
	    if (str[i][j] == '#') {
	      memo[k-i+h][l-j+w] = true;
	    }
	  }
	}
      }
    }
  }

  for (int i = 0; i < 2*h+1; i++) {
    for (int j = 0; j < 2*w+1; j++) {
      if (memo[i][j]) {
	int tcnt = 0;
	bool vis[h][w];
	memset(vis, false, sizeof(vis));
	for (int k = 0; k < h; k++) {
	  for (int l = 0; l < w; l++) {
	    if (str[k][l] != '#' || vis[k][l]) {
	      continue;
	    }
	    vis[k][l] = true;
	    int ny = k+i-h, nx = l+j-w;
	    if (nx >= 0 && ny >= 0 && nx < w && ny < h && str[ny][nx] == '#' && !vis[ny][nx]) {
	      vis[ny][nx] = true;
	      tcnt++;
	    }
	  }
	}
	if (tcnt*2 == cnt) {
	  std::cout << "YES" << std::endl;
	  return 0;
	}
      }
    }
  }

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