from itertools import product

H, W = map(int, input().split())
S = [input() for i in range(H)]

if S == ['.'*W]*H:
  print("NO")
  exit()

for p, q in product(range(H), range(W)):
  if p == q == 0: continue
  T = [list(S[i]) for i in range(H)]
  for i, j in product(range(H-p), range(W-q)):
    if T[i][j] == T[p+i][q+j] == '#':
      T[i][j] = T[p+i][q+j] = '!'
  
  if all('#' not in row for row in T):
    print("YES")
    break
else:
  print("NO")