import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final int H = sc.nextInt();
		final int W = sc.nextInt();
		
		boolean[][] fields = new boolean[H][W];
		for(int i = 0; i < H; i++){
			char[] inputs = sc.next().toCharArray();
			for(int j = 0; j < W; j++){
				fields[i][j] = inputs[j] == '#';
			}
		}
		
		boolean[][] checked = new boolean[H][W];
		
		for(int dy = 0; dy < H; dy++){
			for(int dx = 0; dx < W; dx++){
				if(dx == 0 && dy == 0){ continue; }
				
				for(int i = 0; i < H; i++){
					for(int j = 0; j < W; j++){
						checked[i][j] = false;
					}
				}
				
				for(int y = 0; y < H - dy; y++){
					for(int x = 0; x < W - dx; x++){
						final int nx = x + dx;
						final int ny = y + dy;
						
						if(checked[y][x] || checked[ny][nx]){ continue; }
						if(fields[y][x] && fields[ny][nx]){
							checked[y][x] = checked[ny][nx] = true;
						}
					}
				}
				
				boolean flg = true;
				for(int i = 0; i < H; i++){
					for(int j = 0; j < W; j++){
						if(fields[i][j] && !checked[i][j]){
							flg = false;
						}
					}
				}
				
				if(flg){
					System.out.println("YES");
					return;
				}
			}
		}
		
		System.out.println("NO");
	}
	
}