#include <iostream>
#include <algorithm>
using namespace std ;
long long n , a[1000001] ;
long long sum , cnt;
bool cmp ( int a , int b ) {
	return a>b ;
}
int main () {
	cin >> n ;
	for ( int i = 1 ; i <= n ; i ++ ) cin >> a[i] ;
	sort ( a+1 , a+n+1 , cmp ) ;
	for ( int i = 1 ; i <= n ; i ++ ) {
		if ( (sum+a[i])*1.0/i*(sum+a[i]) > sum*1.0/i*sum ) sum += a[i] , cnt ++ ;
	}
	printf("%.8lf" , sum*1.0/cnt*sum );
	return 0 ;
}