#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define ALL(v) v.begin(),v.end()
#define debug(x) cerr << #x << ": " << x << endl;
const ll MOD = 1e9+7;
const ll INF = 1LL << 60;
void Yes(bool flag) { cout << (flag ? "Yes" : "No") << endl; }
using pii = pair<int, int>;
template<class F, class S>
ostream& operator << (ostream& os, pair<F,S> p) {
    return os << '(' << p.first << ',' << p.second << ')';
}
template<class Iter>
void print(Iter beg, Iter end) {
    for (Iter itr = beg; itr != end; ++itr) {
        cerr << *itr << ' ';
    }
    cerr << endl;
}

int N;
vector<int> A,B;

int main() {
    cin >> N;
    A.resize(N);
    B.resize(N);
    for (auto& a : A) cin >> a;
    for (auto& b : B) cin >> b;
    sort(ALL(A));
    sort(ALL(B));

    int all = 0, win = 0;
    do {
        do {
            ++all;
            int cnt = 0;
            for (int i = 0; i < N; ++i) {
                if (A[i] > B[i]) ++cnt;
            }
            if (cnt > N / 2) ++win;
        } while (next_permutation(ALL(B)));
    } while (next_permutation(ALL(A)));
    cout << fixed << setprecision(6) << (double)win / all << endl;
}