#include <iostream>
#include <vector>
#include <limits.h>
#include <algorithm>
#include <string>
#include <math.h>
#include <limits.h>
#include <queue>
#include <map>
#include <set>
#include <iomanip>
#include <bitset>
#include <cassert>
#include <random>
#include <functional>
#include <stack>
#include <iomanip>
#include <cassert>
//#include <boost/multiprecision/cpp_int.hpp>
#include <complex>
#include <cstdio>
#include <list>
#include <bitset>

//< in.txt > out.txt
using namespace std;
//std::ios::sync_with_stdio(false);
//std::cin.tie(0);
const long long MOD = 1e9 + 7;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ld, ll> pdl;
typedef pair<ld, ld> pdd;
typedef vector<ll> VLL;
typedef vector<VLL> VVLL;
//typedef boost::multiprecision::cpp_int bigint;

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	ll N;
	cin >> N;
	VLL A(N);
	VLL B(N);
	for (ll n = 0; n < N; n++)cin >> A[n];
	for (ll n = 0; n < N; n++)cin >> B[n];
	VLL VA(N);
	for (ll n = 0; n < N; n++)VA[n] = n;
	ll ans = 0;
	do {
		VLL VB(N);
		for (ll n = 0; n < N; n++)VB[n] = n;
		do {
			ll a = 0;
			ll b = 0;
			for (ll n = 0; n < N; n++) {
				if (A[VA[n]] > B[VB[n]])a++;
				else if (A[VA[n]] < B[VB[n]])b++;
				else {
					a++;
					b++;
				}
			}
			if (a > b)ans++;
		} while (next_permutation(VB.begin(), VB.end()));
	} while (next_permutation(VA.begin(), VA.end()));
	ll M = 1;
	for (ll n = N; n >= 1; n--)M *= n;
	M *= M;
	cout << setprecision(12) << (ld)ans / M << "\n";
	return 0;
}