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

int main() {
	int H, W;
	string ans = "NO";
	cin >> H >> W;
	vector<string> board(H);
	for (int i = 0; i < H; i++)
	{
		cin >> board[i];
	}
	for (int i = -H; i <= H; i++)
	{
		for (int j = -W; j <= W; j++)
		{
			if (i == 0 && j == 0) continue;
			vector<vector<int>> check(H, vector<int>(W));
			bool flag = true;
			int count = 0;
			for (int k = 0; k < H; k++)
			{
				for (int l = 0; l < W; l++)
				{
					if (board[k][l] == '#' && !check[k][l]){
						count++;
						check[k][l] = true;
						int nk = k + i;
						int nl = l + j;
						if (nk < 0 || nk >= H || nl < 0 || nl >= W){
							flag = false;
							break;
						}
						if (board[nk][nl] == '#' && !check[nk][nl]){
							check[nk][nl] = true;
						}
						else{
							flag = false;
							break;
						}
						
					}
				}
			}
			if (count == 0) flag = false;
			if (flag) ans = "YES";
		}
	}
	cout << ans << endl;
}