#include <bits/stdc++.h>
using namespace std;
int main(int argc, const char *argv[]) {
  int n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double>> q;
  for (int i = 0; i < n; i++) {
    double n;
    cin >> n;
    q.push(n);
  }
  while (q.size() > 1) {
    int fst = q.top();
    q.pop();
    int snd = q.top();
    q.pop();
    q.push((fst + snd) / 2);
  }
  cout << q.top() << "\n";
  return 0;
}
