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

int factorial(int x) {
	if (x == 0) return 1;
	return x * factorial(x - 1);
}

int main() {
	int n;
	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(a.begin(), a.end());

	int top = 0;
	do {
		int tmp = 0;
		for (int i = 0; i < n; i++) tmp += (a[i] > b[i]);

		if (tmp > n - tmp) top++;
	} while (next_permutation(a.begin(), a.end()));

	cout << fixed << setprecision(8) << (double) top / factorial(n) << '\n';
}