while True:
  h,w = map(int, input().split())
  if h == 0 and w == 0:
    break
  else:
    for j in range(h):
      for i in range(w):
        if (i+j)%2 == 0:
          print("#", end="")
        else:
          print(".", end="")
      print()
    print()
