#include <bits/stdc++.h>
using namespace std;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);  
	
	int h, w;
	cin >> h >> w;
	vector<vector<char>> g(h, vector<char>(w));
	for(int i = 0; i < h; i++) {
		for(int j = 0; j < w; j++) {
			cin >> g[i][j];
		}
	}
	string ans = "NO";
	for(int i = -h; i <= h; i++) {
		for(int j = -w; j <= w; j++) {
			if(i == 0 && j == 0) continue;
			vector<vector<int>> p(h, vector<int>(w, 0));
			bool can = true;
			int cnt = 0;
			for(int k = 0; k < h; k++) {
				for(int l = 0; l < w; l++) {
					if(g[k][l] == '#' && !p[k][l]) {
						cnt++;
						int dh = k + i;
						int dw = l + j;
						if(dh < 0 || dh >= h || dw < 0 || dw >= w) {
							can = false;
							break;
						}
						if(g[dh][dw] == '#' && !p[dh][dw]) {
							p[dh][dw]++;
						} else {
							can = false;
							break;
						}
					}
				}
			}
			if(!cnt) can = false;
			if(can) ans = "YES";
		}
	}
	cout << ans << endl;
	return 0;	
}