#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> vec(3);
  for (int i = 0; i < n; i++) {
    double v;
    cin >> v;
    vec.at(i) = v;
  }
  for (int i = 0; i < n - 1; i++) {
    sort(vec.begin(), vec.end());
    reverse(vec.begin(), vec.end());
    double num;
    num = (vec.at(vec.size() - 1) + vec.at(vec.size() - 2)) / 2;
    vec.pop_back();
    vec.pop_back();
    vec.push_back(num);
  }
  cout << vec.at(0) << endl;
}
