#include <iostream>
#include <vector>
#include <iomanip>
#include <algorithm>

using namespace std;

double solve(vector<int>& a, vector<int>& b, int depth){
    int cnt = 0;
    int won = 0;
    int N = a.size();
    vector<int> parm(N);
    for(int i = 0; i < N; i++){
        parm[i] = i;
    }
    do{
        vector<int> parm2(N);
        for(int i = 0; i < N; i++){
            parm2[i] = i;
        }
        do{
            int cnt1 = 0, cnt2 = 0;
            for(int i = 0; i < N; i++){
                if(a[parm[i]] > b[parm2[i]]) cnt1++;
                if(a[parm[i]] < b[parm2[i]]) cnt2++;
            }
            if(cnt1 > cnt2) won++;
            cnt ++;
        }while(next_permutation(parm2.begin(), parm2.end()));
    }while(next_permutation(parm.begin(), parm.end()));
    return double(won) / cnt;
}



int main(){
    int N;
    cin >> N;
    vector<int> a(N);
    vector<int> b(N);
    for(int i = 0; i < N; i++){
        cin >> a[i];
    }
    for(int i = 0; i < N; i++){
        cin >> b[i];
    }
    cout << setprecision(13) << solve(a, b, 0) << endl;
    return 0;
}