#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <map>
#include <queue>
using ll = long long;
using namespace std;

vector<int> A, B;

int main(void)
{
    int N;
    cin >> N;

    for (int i = 0; i < N; ++i)
    {
        int a;
        cin >> a;
        A.push_back(a);
    }
    for (int i = 0; i < N; ++i)
    {
        int b;
        cin >> b;
        B.push_back(b);
    }
    sort(A.begin(), A.end());
    sort(B.begin(), B.end());

    int cnt = 0;
    do
    {
        do
        {
            int win = 0, lose = 0;
            for (int i = 0; i < N; ++i)
            {
                if (A[i] > B[i])
                    win++;
                else
                    lose++;
            }
            if (win > lose)
                cnt++;
        } while (next_permutation(A.begin(), A.end()));

    } while (next_permutation(B.begin(), B.end()));

    for (int i = N - 1; i >= 1; --i)
        N *= i;

    N *= N;
    cout << fixed << setprecision(3) << (double)cnt / (double)N << endl;
    return 0;
}