#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  vector<double> a(n);
  a.at(0) = 1 / 2;
  cin >> v.at(0);
  for (int i = 1; i < n - 1; i++) {
    cin >> v.at(i);
    a.at(i) = a.at(i - 1) / 2;
  }
  cin >> v.at(n - 1);
  a.at(n - 1) = a.at(n - 2);
  sort(v.begin(), v.end());
  sort(a.begin(), a.end());
  double V = 0;
  for (int i = 0; i < n; i++) {
    V += a.at(i) * v.at(i);
  }
  cout << V << endl;
}
