#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <map>
#include <list>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <iomanip>
#define INF 1050000000
#define SIZE 32
#define MOD 1000000007

using namespace std;

int main(void)
{
	int N, n;
	int A[SIZE], B[SIZE];
	int cnt = 0;
	int win = 0;

	cin >> N;
	n = 1;

	for (int i = 0; i < N; i++) {
		n *= 2;
	}

	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}
	for (int i = 0; i < N; i++) {
		cin >> B[i];
	} 

	sort(A, A + N);

	do {
		cnt = 0;
		for (int i = 0; i < N; i++) {
			if (A[i] > B[i]) {
				cnt++;
			}
			
		}
		if (cnt > N / 2) win++;
	} while (next_permutation(A, A + N));

	int x = 1;
	for (int i = 1; i <= N; i++) {
		x *= i;
	}

	cout << (double)win / (double)x << endl;

	return (0);
}