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