while True:
  (H, W) = [int(x) for x in input().split()]
  if H == H == 0:
    break

  for hc in range(H):
    for wc int range(W):
      if (hc + wc) % 2 == 0:
        print('#', end ='')
      else:
        print('.', end ='')
    print()
  print()