def mp(h, w) :
	for i in range(h):
		for j in range(w):
			if ( (i+j) % 2 == 0):
				print("#", end = '')
			else:
				print('.', end = '')
		print()
	print()




while True:
	h, w = map(int, input().split())
	if h == 0 and w == 0 : break
	mp(h, w)
