while True:
	a,b = map(int, raw_input().split())
	if a + b == 0: break
	for i in range(a):
		if i % 2 == 0:
			tmp = '#.' * (b / 2) 
			tmp += '#' if b % 2 == 1 else ""
		else:
			tmp = '.#' * (b / 2)
			tmp += '.' if b % 2 == 1 else ""
		print tmp
	print 