#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
#include <time.h>
//#include "util.h"

using namespace std;
typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define all(x) (x).begin(), (x).end()


template <typename _KTy, typename _Ty>
ostream& operator << (ostream& ostr, const pair<_KTy, _Ty>& m) {
	cout << "{" << m.first << ", " << m.second << "}";
	return ostr;
}

template <typename _Ty>
ostream& operator << (ostream& ostr, const vector<_Ty>& v) {
	if (v.empty()) {
		cout << "{ }";
		return ostr;
	}
	cout << "{" << v.front();
	for (auto itr = ++v.begin(); itr != v.end(); itr++) {
		cout << ", " << *itr;
	}
	cout << "}";
	return ostr;
}

template <typename _Ty>
ostream& operator << (ostream& ostr, const set<_Ty>& s) {
	if (s.empty()) {
		cout << "{ }";
		return ostr;
	}
	cout << "{" << *(s.begin());
	for (auto itr = ++s.begin(); itr != s.end(); itr++) {
		cout << ", " << *itr;
	}
	cout << "}";
	return ostr;
}

int fact(int n)
{
	int res = 1;
	for (int i = 1; i <= n; i++) res *= i;
	return res;
}

int yuki0133() 
{
	int N, wg = 0;
	cin >> N;
	vector<int> A(N), B(N);
	for (int i = 0; i < N; i++) cin >> A[i];
	for (int i = 0; i < N; i++) cin >> B[i];
	sort(all(A));
	sort(all(B));

	do {
		do {

			int w = 0;
			for (int i = 0; i < N; i++)
				if (A[i] > B[i]) w++;
			if (w > N / 2) wg++;

		} while (next_permutation(all(B)));
	} while (next_permutation(all(A)));
	
	cout << (double)wg / (fact(N) * fact(N)) << endl;

	return 0;
}

int main()
{
	//clock_t start, end;
	//start = clock();

	yuki0133();

	//end = clock();
	//printf("%d msec.\n", end - start);

	return 0;
}