a, b = map(int, input().split())
while a > 0 or b > 0:
	for i in range(a):
		for j in range(b):
			if (i + j) % 2 == 0:
				print("#", end="")
			else:
				print(".", end="")
			if j == b - 1:
				print("")
	print("")
	a, b = map(int, input().split())

