#include <bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;


int main(){
    int n, match = 0;
    cin >> n;
    vector<int> a(n), b(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) cin >> b[i];
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    int ans = 0;
    do{
        do{
            match++;
            int aw = 0, bw = 0;
            for (int i = 0; i < n; i++){
                if (a[i] > b[i]) aw++;
                else bw++;
            }
            if (aw > bw) ans++;
        }while(next_permutation(b.begin(), b.end()));
    }while(next_permutation(a.begin(), a.end()));
    cout << (double) ans / (double) match << endl;
}