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

int cmp(int a, int b)
{
	return a > b;
}

int main()
{
	long long n, a[300001], k;
	double maxsum = -1.0;
	scanf("%d", &n);
	for (k = 0; k < n; k++)
		scanf("%d", &a[k]);
	sort(a, a + n, cmp);
	for (k = 1; k <= n; k++)
		{
			double sum = 0;
			for (int i = 0; i < k; i++)
				sum += a[i];
			sum = sum / k * sum;
			if (sum > maxsum)
				maxsum = sum;
		}
	printf("%.8lf", maxsum);
}