while True:
	h, w = map(int, raw_input().split())
	if (h == 0) and (w == 0):
		break
	for i in xrange(h):
		line = ""
		for j in xrange(w):
			if ((i%2+j%2)%2 == 0):
				line += "#"
			else:
				line += "."
		print line
	print 