#include <bits/stdc++.h>
using namespace std;
priority_queue<double> que;
int main() {
  int n;
  cin >> n;
  double num;
  for (int i = 1; i <= n; i++) {
    cin >> num;
    que.push(-num);
  }
  while (que.size() > 1) {
    double avg;
    int t = que.top();
    que.pop();
    t += que.top();
    que.pop();
    avg = t / 2.0;
    que.push(avg);
  }
  cout << -que.top() << endl;
  return 0;
}
