#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

#define ull unsigned long long
#define ld long double

template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;
template <class T>
using VVV = V<V<V<T>>>;

#define rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) rep2(i, 0, n)
#define rep1(i, n) rep1(i, 1, n + 1)

// #define repr(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
// #define rep1r(i, n) for (int i = ((int)(n)); i >= 1; i--)

#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()  //

#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define RSORT(x) sort(rall(x));

#define INF (1e9)
#define PI (acos(-1))
#define EPS (1e-7)

// 総数を1000000007（素数）で割った余り
const long long mod = 1e9 + 7;

const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1};
const int dy[] = {1, 0, -1, 0, -1, 1, 1, -1};

ull gcd(ull a, ull b) { return b ? gcd(b, a % b) : a; }
ull lcm(ull a, ull b) { return a / gcd(a, b) * b; }

int fact(int n) {
    if (n == 0) return 1;
    return fact(n - 1) * n;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << std::fixed << std::setprecision(15);
    //    cout << std::setfill('0') << std::setw(2);

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

    sort(all(a));
    int ans = 0;
    do {
        int win = 0;
        rep(i, n) if (a[i] > b[i]) win++;
        if (win > n / 2) ans++;
    } while (next_permutation(all(a)));

    cout << 1. * ans / fact(n) << endl;
    return 0;
}