import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int h = sc.nextInt();
		int w = sc.nextInt();
		boolean[][] field = new boolean[h][w];
		for (int i = 0; i < h; i++) {
		    char[] arr = sc.next().toCharArray();
		    for (int j = 0; j < w; j++) {
		        field[i][j] = (arr[j] == '#');
		    }
		}
		for (int i = 0; i < h; i++) {
		    for (int j = 0; j < w; j++) {
		        if (i == 0 && j == 0) {
		            continue;
		        }
		        boolean[][] tmp = new boolean[h][];
		        for (int k = 0; k < h; k++) {
		            tmp[k] = (boolean[])(field[k].clone());
		        }
		        boolean flag = true;
		        for (int a = 0; a < h && flag; a++) {
		            for (int b = 0; b < w && flag; b++) {
		                if (tmp[a][b]) {
		                    if (a + i >= h || b + j >= w || !tmp[a + i][b + j]) {
		                        flag = false;
		                        break;
		                    }
		                    tmp[a + i][b + j] = false;
		                }
		            }
		        }
		        if (flag) {
		            System.out.println("YES");
		            return;
		        }
		    }
		}
		System.out.println("NO");
	}
}