#include <iostream>
#include <string>

#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define pb push_back
using namespace std;

int main(void)
{
	int h, w;
	cin >> h >> w;
	string s[50], _s[50];
	rep(i,0,h) cin >> s[i];

	int sh = 0;
	rep(i, 0, h) rep(j, 0, w) if(s[i][j] == '#') sh++;
	if(sh%2 || sh<2) { cout << "NO" << endl; return 0; }

	int cnt;
	rep(y,0,h) rep(x,0-w,w) {
		rep(i,0,h) _s[i] = s[i];
		cnt = 0;
		rep(i,0,h) rep(j,0,w) {
			if(i+y >= h || j+x >= w) continue;
			if(i+y < 0 || j+x < 0) continue;
			if(_s[i+y][j+x] == '#' && _s[i][j] == '#') {
				cnt++;
				_s[i+y][j+x] = '.';
				_s[i][j] = '.';
			}
		}
	
		if(sh/2 == cnt) { cout << "YES" << endl; return 0; }
	}

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