#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  priority_queue<double, vector<double>, greater<double> > q;
  int v;
  for (int i = 0; i < N; i++) {
    cin >> v;
    q.push(v);
  }
  int top1, top2;
  for (int i = 0; i < N - 1; i++) {
    top1 = q.top();
    q.pop();
    top2 = q.top();
    q.pop();
    q.push((top1 + top2) / 2.0);
  }
  cout << q.top() << endl;
  return 0;
}
