#include <bits/stdc++.h>
using namespace std;
priority_queue<double, vector<double>, greater<double> > q;
int n;
double a, a1, a2;
double ans;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a, q.push(a);
  while (!q.empty()) {
    a1 = q.top();
    q.pop();
    a2 = q.top();
    q.pop();
    double temp = (double)(a1 + a2) / 2;
    q.push(temp);
    ans = q.top();
  }
  printf("%.6lf", ans);
  return 0;
}
