#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

#define rep(i, r) for(int i = 0; i < (r); ++i)
#define reps(i, s, r) for(int i = (s); i < (r); ++i)
#define fore(i, m2) for(auto &i : m2)
#define vi vector<int>
#define vl vector<ll>
#define pl pair<ll, ll>
#define all(i) (i).begin(), (i).end()
#define fs first
#define sc second

template <class T> bool chmin(T &i, T b) {
    if(i > b) {
        i = b;
        return true;
    }
    return false;
}
template <class T> bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}

const ll INF = LONG_LONG_MAX / 3;
const ll MOD = 1'000'000'007;
const ll MAX = 1e4 + 5;

int main() {

    ll n;
    cin >> n;
    vl a(n), b(n);

    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];

    ld allc = 0.0, cnt = 0.0;

    sort(all(a));
    sort(all(b));

    do {
        do {

            allc++;
            ll win = 0, lose = 0;
            rep(i, n) {
                if(a[i] > b[i])
                    win++;
                else
                    lose++;
            }

            if(win > lose)
                cnt++;
        } while(next_permutation(all(b)));
    } while(next_permutation(all(a)));

    cout << setprecision(10) << cnt / allc << endl;
}