#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	int a[1020190];
	double ans=0;
	double chen,ke;
	double ans1,num;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	sort(a+1,a+1+n);
	reverse(a+1,a+1+n);
	for(int i=1;i<=n;i++)
	{
		ans+=a[i];
		ans1=ans+a[i+1];
		chen=ans*ans/i;
		ke=(ans1*ans1)/(i+1);
		if(chen<ke)
		{
			num=ke;
		}
	}
	printf("%.4lf",num);
	return 0;
}