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

using ldouble = long double;

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> xs(n), ys(n);
    for (auto& x : xs) std::cin >> x;
    for (auto& y : ys) std::cin >> y;
    std::sort(xs.begin(), xs.end());
    std::sort(ys.begin(), ys.end());

    int tot = 0, win = 0;
    do {
        do {
            ++tot;

            int cnt = 0;
            for (int i = 0; i < n; ++i) {
                if (xs[i] > ys[i]) ++cnt;
            }

            if (cnt > n - cnt) ++win;
        } while (std::next_permutation(ys.begin(), ys.end()));
    } while (std::next_permutation(xs.begin(), xs.end()));

    std::cout << std::fixed << std::setprecision(10)
              << ldouble(win) / tot << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}