import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import itertools

H,W = map(int,readline().split())
data = ''.join(read().decode().split())

if not data.count('#'):
    print('NO')
    exit()

def test(a,b):
    if a==b==0:
        return False
    close = [0] * (H*W)
    for x,y in itertools.product(range(H), range(W)):
        ind = W*x + y
        if close[ind]:
            continue
        if data[ind] == '.':
            continue
        x1,y1 = x+a, y+b
        if x1 >= H or y1 < 0 or y1 >= W:
            return False
        ind1 = W*x1 + y1
        if data[ind1] == '.':
            return False
        close[ind] = 1
        close[ind1] = 1
    return True

bl = any(test(a,b) for a in range(51) for b in range(-51,51))
answer = 'YES' if bl else 'NO'
print(answer)