#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <cmath>

using namespace std;

int factorial(int n) {
	if (n == 1) {
		return 1;
	} else {
		return n * factorial(n - 1);
	}
}

int main() {
	int n;

	cin >> n;
	vector<int> a(n, 0), b(n, 0), order(n , 0);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		order[i] = i;
	}
	for (int i = 0; i < n; i++) {
		cin >> b[i];
	}

	int total_win = 0;
	do {
		int wins = 0;
		for (int i = 0; i < n; i++) {
			if (a[i] > b[order[i]]) {
				wins++;
			}
		}
		if (wins > n / 2) {
			total_win++;
		}
	} while (next_permutation(order.begin(), order.end()));

	double ans = 1.0 * total_win / factorial(n);
	printf("%.3f\n", ans);
	return 0;
}