while True :
	H, W = map(int, input().split())
	if(H == 0 & W == 0) :
		break
	else :
		for i in range(H) :
			for j in range(W) :
				if((i + j) % 2 == 0) :
					print("#", end = "")
				else :
					print(".", end = "")
			print()
		print()
