#include <iostream>

using namespace std;

int main() {
	int h, w;
	cin >> h;
	cin >> w;
	int sum = 0;
	char c;
	bool** dp = new bool*[h];

	for (int i = 0; i < h; ++i) {
		dp[i] = new bool[w];
		for (int j = 0; j < w; ++j) {
			cin >> c;
			if (c == '#') {
				++sum;
				dp[i][j] = true;
			}
			else{
				dp[i][j] = false;
			}
		}
	}
	if (sum % 2 == 1) {
		cout << "NO" << endl;
		return 0;
	}
	int count = 0;
	for (int i = 0; i < h; ++i) {
		for (int j = 1; j < w; ++j, count = 0) {
			for (int a = 0; a < h - i; ++a) {
				for (int b = 0; b < w - j; ++b) {
					if (dp[a + i][b + j] && dp[a][b]) {
						++count;
					}
				}
			}
			if (count == sum / 2) {
				cout << "YES" << endl;
				return 0;
			}
		}
		for (int j = -(w - 1); j < 0; ++j, count = 0) {
			for (int a = 0; a < h - i; ++a) {
				for (int b = 0; b < w + j; ++b) {
					if (dp[a + i][b] && dp[a][b - j]) {
						++count;
					}
				}
			}
			if (count == sum / 2) {
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}