Optimal Services

#include <stdio.h>#include <stdlib.h>#include <iostream>#include <algorithm>using namespace std;int main(){int n;int    a[4000];double sum=0;scanf("%d",&n);sum=0;int i;for(i=0;i<n;i++)scanf("%d",&a[i]);sort(a,a+n);for(i=0;i<n;i++){sum+=a[i]*(n-i);}printf("%.2lf\n",sum/n);return 0;}