h,w = map(int,input().split())

while w != 0 and h != 0:
	for j in range(h):
		for i in range(w):
			if (i + (j % 2)) % 2 == 0:
				print("#", end="")
			if (i + (j % 2)) % 2 == 1:
				print(".", end="")
		print()
	print()
	h,w = map(int,input().split())

	