#include <bits/stdc++.h>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <deque>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <ctime>
#include <iterator>
#include <bitset>
#include <numeric>
#include <list>
#include <iomanip>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
typedef pair<int, int> P;
typedef long long ll;
const ll INF = 1e18;
#define mod 998244353
#define submod 1000000007
#define mod_inv2 499122177
#define submod_inv2 500000004
#define pai 3.141592653589
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    vector<int> b(n);
    rep(i, n)
    {
        cin >> a[i];
    }
    rep(i, n)
    {
        cin >> b[i];
    }

    sort(a.begin(), a.end());
    sort(b.begin(), b.end());

    ll all = 0;
    ll win = 0;
    do
    {
        do
        {

            int anum = 0;
            all += 1;
            rep(i, n)
            {
                if (a[i] > b[i])
                {
                    anum += 1;
                }
            }
            if (anum > n - anum)
            {
                win += 1;
            }
        } while (next_permutation(b.begin(), b.end()));
    } while (next_permutation(a.begin(), a.end()));

    double ans = double(win) / double(all);
    cout << fixed << setprecision(15) << ans << endl;
}