#include <bits/stdc++.h>
using namespace std;

int factorial(int n)
{
	int retval = n;
	for(int i = n-1; i >= 1; i--)
		retval *= i;
	return retval;
}

int main()
{
	int n;
	cin >> n;
	vector<int> a(n);
	vector<int> b(n);
	for(int i = 0; i < n; i++)
		cin >> a[i];
	for(int i = 0; i < n; i++)
		cin >> b[i];
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	int ans = 0;
	do{
		int turnWin = 0;
		for(int i = 0; i < n; i++){
			if(a[i] > b[i])
				turnWin++;
		}
		if(turnWin > n/2){
		/*	cout << ans << " a:";
			for(int i = 0; i < n; i++)
				cout << a[i] << " ";
			cout << "b:";
			for(int i = 0; i < n; i++)
				cout << b[i] << " ";
			cout << "\n";*/
			ans++;
		}
	}while(next_permutation(a.begin(), a.end()));

	//cout << ans << "\n";
	cout << (double)ans / factorial(n) << "\n";

	return 0;
}