ans

#include <bits/stdc++.h>
using namespace std;
int s[1005];
bool cmp(int a, int b) {  //排序方式
    return a < b;         //小的在前面
}
int main() {
    int n, i, sum = 0, t = 1;
    double p, c, x;
    cin >> n;
    for (i = 1; i <= n; i++) {
        cin >> s[i];
    }
    sort(s + 1, s + 1 + n, cmp);
    for (i = n ; i >= 1; i--) {
        sum = sum + i * s[t];
        t++;
    }
    p = sum;
    c = n;
    x = p / c;
    printf("%.2lf", x);
    return 0;
}