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

int main()
{
	int n;
	cin >> n;
	int a[n], b[n];
	long long num = 0;
	long long ans = 0;
	for (int i = 0; i < n; i++) cin >> a[i];
	for (int i = 0; i < n; i++) cin >> b[i];
	sort(a, a+n);
	sort(b, b+n);

	do {
		do {
			long long res_a = 0;
			long long res_b = 0;
			for (int i = 0; i < n; i++){
				if (a[i] > b[i]) res_a++;
				else res_b++;
			}
			if (res_a > res_b) ans++;
			num++;
			
		} while (next_permutation(a, a+n));
	} while (next_permutation(b, b+n));

	cout << (double)ans / (double)num << endl;
}