#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> worth(N);
  for (int i = 0; i < N; i++) {
    cin >> worth[i];
  }
  if (N == 2) {
    double min1 = *std::min_element(worth.begin(), worth.end());
    std::vector<double>::iterator minIt1 =
        std::min_element(worth.begin(), worth.end());
    ;
    int minIndex1 = std::distance(worth.begin(), minIt1);
    worth.erase(worth.begin() + minIndex1);
    double min2 = *std::min_element(worth.begin(), worth.end());
    std::vector<double>::iterator minIt2 =
        std::min_element(worth.begin(), worth.end());
    int minIndex2 = std::distance(worth.begin(), minIt2);
    worth.erase(worth.begin() + minIndex2);
    worth.push_back((min1 + min2) / 2.0);
  }
  for (int i = 0; i < N - 1; i++) {
    double min1 = *std::min_element(worth.begin(), worth.end());
    std::vector<double>::iterator minIt1 =
        std::min_element(worth.begin(), worth.end());
    ;
    int minIndex1 = std::distance(worth.begin(), minIt1);
    worth.erase(worth.begin() + minIndex1);
    double min2 = *std::min_element(worth.begin(), worth.end());
    std::vector<double>::iterator minIt2 =
        std::min_element(worth.begin(), worth.end());
    int minIndex2 = std::distance(worth.begin(), minIt2);
    worth.erase(worth.begin() + minIndex2);
    worth.push_back((min1 + min2) / 2.0);
  }
  cout << worth[0] << endl;
  return 0;
}
