///
// File:  133.go
// Author: ymiyamoto
//
// Created on Tue Mar  6 23:44:21 2018
//
package main

import (
	"fmt"
)

var N int

func perm(arr []int) [][]int {
	if len(arr) == 0 {
		return [][]int{}
	}

	per := perm(arr[1:])

	var ret [][]int
	for _, val := range per {
		tmp := make([]int, len(val))
		copy(tmp, val)
		for i := 0; i <= len(tmp); i++ {
			tmp = append(tmp, 0)
			copy(tmp[:i+1], tmp[:i])
			tmp[i] = arr[0]
			ret = append(ret, tmp)
		}
	}
	return ret
}

func main() {
	fmt.Scan(&N)

	A := make([]int, N)
	B := make([]int, N)

	for i := 0; i < N; i++ {
		fmt.Scan(&A[i])
	}

	for i := 0; i < N; i++ {
		fmt.Scan(&B[i])
	}

	permA := perm(A)
	permB := perm(B)

	var winB, winA int
	for i := 0; i < len(A); i++ {
		var a, b int
		for j := 0; j < N; j++ {
			if permA[i][j] > permB[i][j] {
				a++
			} else {
				b++
			}
		}
		if a < b {
			winB++
		} else {
			winA++
		}
	}
	fmt.Println(float64(winA) / float64(winA+winB))
}