#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
	int h, w;
	cin >> h >> w;
	vector<string> s(h);
	int blackCount = 0;
	for (int i = 0; i < h; ++i) {
		cin >> s[i];
		blackCount += count(s[i].begin(), s[i].end(), '#');
	}
	if (blackCount == 0) {
		cout << "NO" << endl;
		return 0;
	}
	vector<string> filled(h);
	for (int offsetY = 0; offsetY < h; ++offsetY) {
		for (int offsetX = 0; offsetX < w; ++offsetX) {
			if (offsetX == 0 && offsetY == 0) {
				continue;
			}
			filled.assign(s.begin(), s.end());
			bool possible = true;
			for (int y = 0; y < h && possible; ++y) {
				for (int x = 0; x < w && possible; ++x) {
					if (filled[y][x] == '#') {
						if ((x + offsetX < w)
							&& (y + offsetY < h)
							&& (filled[y + offsetY][x + offsetX] == '#')) {
							filled[y][x] = 'R';
							filled[y + offsetY][x + offsetX] = 'B';
						} else {
							possible = false;
						}
					}
				}
			}
			if (possible) {
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	for (int offsetY = 0; offsetY < h; ++offsetY) {
		for (int offsetX = 0; offsetX > -w; --offsetX) {
			if (offsetX == 0 && offsetY == 0) {
				continue;
			}
			filled.assign(s.begin(), s.end());
			bool possible = true;
			for (int y = 0; y < h && possible; ++y) {
				for (int x = w - 1; x >= 0 && possible; --x) {
					if (filled[y][x] == '#') {
						if ((x + offsetX >= 0)
							&& (y + offsetY < h)
							&& (filled[y + offsetY][x + offsetX] == '#')) {
							filled[y][x] = 'R';
							filled[y + offsetY][x + offsetX] = 'B';
						} else {
							possible = false;
						}
					}
				}
			}
			if (possible) {
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}