LIST = list(("#", ".")*151)
while True:
  h, w = list(map(int, input().split()))
  if h == w == 0:
    break
  for i in range(h):
    if i % 2 == 0:
      print("".join(LIST[0:w]))
    else:
      print("".join(LIST[1:w+1]))
  print("")
