#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 || blackCount % 2 == 1) {
		cout << "NO" << endl;
		return 0;
	}
	static bool movable[50][50][50][50]; // [cellX][cellY][offsetX][offsetY]
	for (int y = 0; y < h; ++y) {
		for (int x = 0; x < w; ++x) {
			if (s[y][x] == '.') {
				fill(&movable[x][y][0][0], &movable[x][y][49][49] + 1, false);
			} else {
				for (int offsetY = 0; offsetY < h; ++offsetY) {
					for (int offsetX = 0; offsetX < w; ++offsetX) {
						movable[x][y][offsetX][offsetY]
							= (x + offsetX < w)
							&& (y + offsetY < h)
							&& (s[y + offsetY][x + offsetX] == '#');
					}
				}
			}
		}
	}
	for (int offsetY = 0; offsetY < h; ++offsetY) {
		for (int offsetX = 0; offsetX < w; ++offsetX) {
			int movableCount = 0;
			for (int y = 0; y < h; ++y) {
				for (int x = 0; x < w; ++x) {
					if (movable[x][y][offsetX][offsetY]) {
						++movableCount;
					}
				}
			}
			if (movableCount == blackCount / 2) {
				bool overlapped = false;
				for (int y = 0; y < h && !overlapped; ++y) {
					for (int x = 0; x < w && !overlapped; ++x) {
						if (movable[x][y][offsetX][offsetY]
							&& movable[x + offsetX][y + offsetY][offsetX][offsetY]) {
							overlapped = true;
						}
					}
				}
				if (!overlapped) {
					cout << "YES" << endl;
					return 0;
				}
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}