#include<iostream>
#include<iomanip>
#include<string>
#include<cmath>
#include<stdio.h>
#include<cstdio>
using namespace std;
double a[10000005],b[10000005];
int main(){
	double n,sum1=0,sum2=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		sum1+=a[i];
	}
	sum1*=3;
	for(int i=1;i<=n;i++){
		cin>>b[i];
		sum2+=b[i];
	}
	sum2*=2;
	double sum3=0;
	for(int i=1;i<=n;i++){
		sum3=sum3+(a[i]-b[i]);
	}
	printf("%.6lf",(double)((sum1-sum2)/sum3));
	return 0;
}