
while True:
	H,W = map(int,input().split())
	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("")