package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	aa := make([]int, n)
	bb := make([]int, n)
	for i := 0; i < n; i++ {
		aa[i] = getNextInt(scanner)
	}
	for i := 0; i < n; i++ {
		bb[i] = getNextInt(scanner)
	}
	p := 1
	for i := 0; i < n; i++ {
		p *= i + 1
	}
	pm := newPermutation(n)
	var ans int
	for i := 0; i < p; i++ {
		a := pm.get(i)
		for j := 0; j < p; j++ {
			w := 0
			b := pm.get(j)
			for k := 0; k < n; k++ {
				if aa[a[k]-1] > bb[b[k]-1] {
					w++
				}
			}
			if w > n-w {
				ans++
			}
		}
	}
	one := float64(ans) / float64(p*p)

	fmt.Fprintln(writer, one)
}

type permutation []int

func newPermutation(n int) permutation {
	p := make(permutation, n)
	p[0] = 1
	for i := 1; i < n; i++ {
		p[i] = p[i-1] * i
	}
	return p
}
func (p permutation) index(a []int) int {
	n := len(p)
	ans := 0
	used := make([]bool, n)
	for i := 0; i < n; i++ {
		sum := 0
		used[a[i]-1] = true
		for j := a[i] - 1; j >= 0; j-- {
			if used[j] {
				continue
			}
			sum++
		}
		ans += sum * p[n-1-i]
	}
	return ans
}
func (p permutation) get(index int) []int {
	n := len(p)
	ans := make([]int, n)
	used := make([]bool, n)
	for i := 0; i < n; i++ {
		ans[i] = index / p[n-1-i]
		index %= p[n-1-i]
	}
	for i := 0; i < n; i++ {
		for j := 0; j < n; j++ {
			if used[j] {
				continue
			}
			if ans[i] == 0 {
				ans[i] = j + 1
				used[j] = true
				break
			}
			ans[i]--
		}
	}
	return ans
}