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