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

int main() {
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    for (int i = 0; i < n; i++) cin >> a.at(i);
    for (int i = 0; i < n; i++) cin >> b.at(i);
    int match = 0, win = 0;
    sort(a.begin(), a.end());
    do {
        sort(b.begin(), b.end());
        do {
            int win_local = 0;
            for (int i = 0; i < n; i++) {
                if (a.at(i) > b.at(i)) win_local++;
            }
            if (win_local > n / 2) win++;
            match++;
        } while (next_permutation(b.begin(), b.end()));
    } while (next_permutation(a.begin(), a.end()));
    cout << 1.0 * win / match << endl;
}