#!/usr/bin/env python
# -*- coding: utf-8 -*-
from itertools import permutations

n = int(input())
a = [int(i) for i in input().split()]
b = [int(i) for i in input().split()]

cnt = win = 0

for i in permutations(a, n):
    cnt += 1
    w = 0
    for x, y in zip(i, b):
        if x > y: w += 1
        elif x < y: w -= 1
    if w > 0: win += 1

print(win / cnt)