#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
// using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define rrep1(i, n) for (int i = n; i >= 1; i--)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define eb emplace_back
#define fi first
#define se second
template <class T> using V = vector<T>;
template <class T> using VV = V<V<T>>;
typedef long long int ll;
typedef pair<int, int> P;
// typedef modint1000000007 mint;

void speedUpIO() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
}

template <class T> bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T> bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
/*--------------------------------------------------*/
const int INF = 1e9;
// const ll INF = 1e18;
const int MAX = 1e6;

void solve() {
    int n;
    cin >> n;
    V<int> a(n), b(n);
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    VV<int> bs;
    sort(all(a));
    sort(all(b));
    double ans = 0;
    int cnt = 0;
    do {
        cnt++;
        int abw = 0;
        int pc = 0;
        do {
            pc++;
            int aw = 0;
            rep(i, n) {
                if (a[i] > b[i]) aw++;
            }
            if (aw > n - aw) abw++;
        } while (next_permutation(all(b)));
        ans += (double)abw / pc;
    } while (next_permutation(all(a)));
    ans /= cnt;
    printf("%.10f\n", ans);
}

int main() {
    // speedUpIO();
    solve();
    return 0;
}