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 di, dj in product(range(H), range(1-W, W)):
  if di == 0 >= dj: continue
  T = [list(S[i]) for i in range(H)]
  for i, j in product(range(H), range(W)):
    i2, j2 = i + di, j + dj
    if H > i2 >= 0 <= j2 < W \
    and T[i][j] == T[i2][j2] == '#':
      T[i][j] = T[i2][j2] = '!'
  
  if all('#' not in row for row in T):
    print("YES")
    break
else:
  print("NO")