#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> u(N);
  for (int i = 0; i < N; ++i) {
    cin >> u[i];
  }
  sort(u.begin(), u.end());
  double num;
  double num2 = 0.0;
  for (int i = 0; i < N; ++i) {
    num = (num2 + u[i + 1]) / 2;
    num2 = num2 + num;
  }
  cout << num2 << endl;
}
