#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
	int n;
	cin >> n;
	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(a, a+n);

	long long int A, ALL;
	A = ALL = 0;
	do {
		sort(b, b+n);
		do {
			int cnt = 0;
			for (int i = 0; i < n; i++){
				if (a[i] > b[i]) cnt++;
				else if (b[i] > a[i]) cnt--;
			}
			if (cnt > 0) A++;
			ALL++;
		} while (next_permutation(b, b+n));
	} while (next_permutation(a, a+n));
	printf("%.10lf\n", (double)A / (double)ALL);
}