package main

import (
	"fmt"
	"sort"
)

var as, bs []int
var awin int

func dfs(pa, pb int) {
	n := len(as)

	if n == 0 {
		if pa > pb {
			awin++
		}
		return
	}

	for i := 0; i < n; i++ {
		for j := 0; j < n; j++ {
			sort.Ints(as)
			sort.Ints(bs)
			a, b := as[i], bs[j]
			as[i], as = as[n-1], as[:n-1]
			bs[j], bs = bs[n-1], bs[:n-1]
			sort.Ints(as)
			sort.Ints(bs)
			if a > b {
				dfs(pa+1, pb)
			} else {
				dfs(pa, pb+1)
			}
			as = append(as, a)
			bs = append(bs, b)
		}
	}
}

func p(n int) int {
	if n == 0 {
		return 1
	}
	return n * p(n-1)
}

func main() {
	var n int
	fmt.Scan(&n)
	as, bs = make([]int, n), make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&as[i])
	}
	for i := 0; i < n; i++ {
		fmt.Scan(&bs[i])
	}
	dfs(0, 0)
	fmt.Printf("%f\n", float64(awin)/float64(p(n)*p(n)))
}