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

int main() {
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    int total = 0, win_a = 0;
    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());
    sort(b.begin(), b.end());
    do {
        vector<int> b_ = b;
        do {
            total++;
            int win_a_tmp = 0;
            for (int i = 0; i < n; i++) {
                if (a[i] > b_[i]) win_a_tmp++;
            }
            if (win_a_tmp > (n / 2)) win_a++;
        } while (next_permutation(b_.begin(), b_.end()));
    } while (next_permutation(a.begin(), a.end()));

    cout << double(win_a) / total << endl;
    return 0;
}