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

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