rt

#include<bits/stdc++.h>
using namespace std;
//(每一科的满分之和*3-每一科的实际得分之和*2)÷每科所扣除分数的和
int main()
{
	int n,a=0,b=0,c=0,s=0;
	cin>>n;
	for (int i=0;i<n;i++)
	{
		cin>>s;
		a+=s;
		 
	}
	s=0;
	for (int i=0;i<n;i++)
	{
		cin>>s;
		b+=s;
	}
	
	cout<<fixed<<setprecision(6)<<(a*3-b*2)/(a-b);
	
}