while True:
  h, w = [int(i) for i in input().split()]
  if h == 0 and w == 0:
    break
  for i in range(h):
    for j in range(w):
        print('#' if (i % 2 == 0 and j % 2 == 0) or (i % 2 != 0 and j % 2 != 0) else '.', end='')
    print()
  print()
