while True:
	H,W = list(map(int, input().split()))
	if (H == 0 and W == 0):
		break
	else:
		for n in range(H):
			s = ""
			for m in range(W):
				if ((n % 2 == 1) and (m % 2 == 0)) or5 6 ((n % 2 == 0) and (m % 2 == 1)):
					s += "."
				else:
					s += "#"
			print(s)
		print("")