while True:
	nums = list(map(int, input().split(" ")))
	h = nums[0]
	w = nums[1]
	if h == 0 and w == 0:
		break

	for i in range(h):
		for j in range(w):
			if (i + j) % 2 == 0:
				print("#", end="")
			else:
				print(".", end="")
		print("")
	
	print("")
