package division;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int h = sc.nextInt();
		int w = sc.nextInt();
		char[][] map = new char[h][];
		for(int i=0;i<h;i++) {
			map[i] = sc.next().toCharArray();
		}
		System.out.println(solve(h,w,map) ? "YES" : "NO");
	}

	public static boolean solve(int h,int w,char[][] map) {
		boolean[][] painted = new boolean[h][w];
		for(int di=0;di<h;di++) {
			LOOP: for(int dj=-w+1;dj<w;dj++) {
				if (di == 0 && dj <= 0) {
					continue;
				}
				for(int i=0;i<h;i++) {
					Arrays.fill(painted[i], false);
				}
				int count = 0;
				for(int i=0;i<h;i++) {
					for(int j=0;j<w;j++) {
						if (map[i][j] == '#' && !painted[i][j]) {
							int ni = i + di;
							int nj = j + dj;
							if (ni < 0 || ni >= h || nj < 0 || nj >= w) {
								continue LOOP;
							}
							if (map[ni][nj] != '#' || painted[i][j]) {
								continue LOOP;
							}
							painted[i][j] = painted[ni][nj] = true;
							count++;
						}
					}
				}
				if (count >= 1) {
					return true;
				}
			}
		}
		return false;
	}
}