import itertools

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

A_win = 0
B_win = 0

for A_play in itertools.permutations(A):
	for B_play in itertools.permutations(B):
		tmp_A_win = 0
		tmp_B_win = 0
		for i in range(N):
			if A_play[i] > B_play[i]:
				tmp_A_win += 1
			else:
				tmp_B_win += 1
		if tmp_A_win > tmp_B_win:
			A_win += 1
		else:
			B_win += 1

print(A_win/(A_win+B_win))