#include <bits/stdc++.h>
#define int long long
using namespace std;

double ans;
double sum;
double cnt;

signed main ()
{
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
	int n;
	cin >> n;
	int a [1000005],b [1000005];
	for (int i = 1;i <= n;i ++)
	{
		cin >> a [i];
		ans += a [i];
	}
	for (int i = 1;i <= n;i ++)
	{
		cin >> b [i];
		sum += b [i];
	}
	for (int i = 1;i <= n;i ++)
	    cnt += a [i] - b [i];
	printf ("%.6lf",(ans * 3 - sum * 2) / cnt);
	return 0;
}