while True:
  h, w = map(int, raw_input().split())
  if (h == 0 and w == 0):
    break
  wi = int(w)
  for i in range(0,h):
    if i % 2 == 0:
      if w % 2 == 0: print('#.' * (wi / 2))
      else: print('#.' * (wi / 2) + '#')
    else:
      if w % 2 == 0: print('.#' * (wi / 2))
      else: print('.#' * (wi / 2) + '.') 
  print

  