#include"bits/stdc++.h"
using namespace std;
using ll = long long;
using ld = long double;
#define rep(i,m,n) for(ll i=(ll)m;i<(ll)n;i++)
#define Endl endl
#define pr(i,j) make_pair(i,j) 
const ll mod = 998244353;
const ll inf = 5e18;
const ld pi = 3.14159265358979;
int main() {
	ll h, w;
	cin >> h >> w;
	vector<string>m(h);
	rep(i, 0, h)cin >> m[i];
	bool f = false;
	rep(i, 0, h) {
		rep(j, 0, w) {
			if (m[i][j] == '#')f = true;
		}
	}
	if (!f) {
		cout << "NO" << endl; 
		return 0;
	}
	rep(i, -70, 70) {
		rep(j, -70, 70) {
			if (i == 0 && j == 0)continue;
			vector<string>copy = m;
			rep(k, 0, h) {
				rep(l, 0, w) {
					if (copy[k][l] == '#') {
						if (!(0 <= k + i && k + i < h))goto next;
						if (!(0 <= l + j && l + j < w))goto next;
						if (copy[k + i][l + j] == '#') {
							copy[k + i][l + j] = '.';
							copy[k][l] = '.';
						}
						else goto next;
					}
				}
			}
			cout << "YES" << endl;
			return 0;
			next:{}
		}
	}
	cout << "NO" << endl;
}