1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdio>
 4 using namespace std;
 5 long long a[100001],b[101001],sum[100001],summ[100001];
 6 long long ans=0,cs;
 7 int n;
 8 int main ()
 9 {
10     
11     cin>>n;
12     for (int i=1;i<=n;i++)
13         cin>>a[i];
14     for (int i=1;i<=n;i++)
15         cin>>b[i];
16     sort(a+1,a+1+n);
17     sort(b+1,b+1+n);
18     for (int i=1;i<=n;i++)
19     {
20         sum[i]=sum[i-1]+b[i];
21         summ[i]=summ[i-1]+b[i]*b[i];
22     }
23     long long j=0;
24     for (int i=1;i<=n;i++)
25     {
26         while (a[i]>b[j]&&j<=n) j++;
27         ans+=(j-1)*a[i]*a[i]-2*a[i]*sum[j-1]+summ[j-1];
28         ans-=((n-j+1)*a[i]*a[i]-2*a[i]*(sum[n]-sum[j-1])+summ[n]-summ[j-1]);
29     }
30     double s=(double)(ans)/(double)(n);
31     printf("%.1f",s);
32 }