#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;

int getIndexOf(double a, vector<double> y)
{
    int count=1;
    for (int j=0; j<y.size(); ++j)
    {
        if (a==y[j])
            break;
        else
            count++;
    }
    return count;
}

vector<int> getRank(vector<double> x)
{
    vector<int> xVar(x.size());
    vector<double> x_sorted(x.size());
    partial_sort_copy(begin(x), end(x), begin(x_sorted), end(x_sorted));
    for(int i=0; i<x.size(); ++i)
    {
        int index=getIndexOf(x[i], x_sorted);
        xVar[i]=index;
    }
    return xVar;
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    
    vector<double> x,y;
    double num=0;
    for(int i=0; i<n; ++i){
        cin>>num;
        x.push_back(num);
    }
    
    for(int i=0; i<n; ++i){
        cin>>num;
        y.push_back(num);
    }
    vector<int> rankX=getRank(x);
    vector<int> rankY=getRank(y);
    
    double r=0;
    for (int i=0; i<n; ++i)
    {
        r+=pow((rankX[i]-rankY[i]),2.);
    }
    cout<<fixed<<setprecision(3);
    cout<<1-6*r/(n*n*n-n);
    return 0;
}