#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double>> pq;
  double value;
  for (int i = 0; i < n; ++i) {
    cin >> value;
    pq.push(value);
  }
  for (int i = 0; i < n - 1; ++i) {
    int v1 = pq.top();
    pq.pop();
    int v2 = pq.top();
    pq.pop();
    pq.push((v1 + v2) / 2.0);
  }
  cout << pq.top() << '\n';
}
