H,W=map(int,input().split())
t = 0
while not ( H == 0 and W == 0 ):
	for h in range(H):
		line = ""

		ptn=["#","."]

		for w in range(W):
			line += ptn[(h+w)%2]

		print(line)

	print("")
	t+=1
	H,W=map(int,input().split())

