#include <bits/stdc++.h> 

using namespace std;

int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, t;
    vector <int> a, b;

    cin >> n;

    for (int i = 0; i < n; i++)
    {
        cin >> t;
        a.push_back(t);
    }

    for (int i = 0; i < n; i++)
    {
        cin >> t;
        b.push_back(t);
    }

    double total = 0;
    double res = 0;

    sort(a.begin(), a.end());

    do
    {
        sort(b.begin(), b.end());
        do
        {
            int scoreA = 0;
            int scoreB = 0;
            for (int i = 0; i < n; i++)
            {
                if (a[i] > b[i])
                {
                    scoreA++;
                }
                else
                {
                    scoreB++;
                }
            }
            if (scoreA > scoreB)
            {
                res++;
            }
            total++;
        } while (next_permutation(b.begin(), b.end()));
    } while (next_permutation(a.begin(), a.end()));

    cout << fixed;
    cout.precision(9);

    cout << (res / total) << '\n';

    return 0;
}