#!/usr/bin/env python3
# -*- coding: utf-8-*-
import numpy as np
def f(i, j, h, w, tl):
    for a in range(h):
        for b in range(w):
            if tl[a, b] == "#":
                if a+i >= h:
                    return False
                elif b+j >= w:
                    return False
                elif b+j < 0:
                    return False
                elif tl[a+i, b+j] == "#":
                    tl[a,b] = "."
                    tl[a+i, b+j] = "."
                else:
                    return False
    return True

if __name__ == '__main__':
    h, w = map(int, input().split(" "))
    l = []
    for i in range(h):
        l.append(list(input()))
    l = np.array(l)
    if not "#" in l:
        print("NO")
        exit()
    for i in range(h):
        for j in range(-w+1, w):
            if i == 0 and j == 0:
                continue
            flag = f(i, j, h, w, np.copy(l))
            if flag:
                print("YES")
                exit()
    print("NO")