#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
using namespace std;

int main() {
    int n;
    cin >> n;
    priority_queue<double, vector<double>, greater<double>> q;
    rep(i,n) {
        double a;
        cin >> a;
        q.push(a);
    }

    double ans = 0;
    rep(i,n-1) {
        double q1 = q.top(); q.pop();
        double q2 = q.top(); q.pop();
        double q_mean = (q1 + q2) / 2;
        ans += q_mean;
        q.push(q_mean);
    }

    printg("%.10f",q.top())
    return 0;
}