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

int a[10000000];

bool cmp(int x,int y)
{
    return x > y;
}

int main()
{
    int n;
    cin >> n;
    for (int i = 1;i <= n;i++)
    {
        cin >> a[i];
    }
    sort(a + 1,a + n + 1,cmp);
    
    double ans = 0;
    long long eat = 0;
    long long k = 0;
    for (int i = 1;i <= n;i++)
    {
        int e = eat + a[i];
        if (1.0 * e*e / (k + 1) > ans)
        {
            ans = 1.0 * e * e / (k + 1);
            k++;
            eat += a[i];
        }
        else break;
    }
    cout << setprecision(8) << fixed << ans << endl;
    return 0;
} ```