#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

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());

    double ret = 0;
    do {
        int now = 0;
        for (int i = 0; i < n; i++) {
            if (a[i] > b[i])now++;
        }
        if (now > n - now)ret++;
    } while (next_permutation(a.begin(), a.end()));

    double fact = 1;
    for (int i = 1; i <= n; i++)fact *= i;
    cout << ret / fact << endl;
    return 0;
}