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