def readfile(filename, directed = None):
	with open(filename) as f:
		n = int(f.readline())
		res = [set() for i in range(n)]
		s = f.readline()
		while s != '':
			x, y = tuple([int(z) for z in s.split()])
			res[x].add(y)
			if not directed:
				res[y].add(x)
			s = f.readline()
	return n, res

n, G = readfile('input.txt', True)
print(n, G)