#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<long double> u(N);
  for (int i = 0; i < (int)(N); i++) {
    cin >> u.at(i);
  }
  sort(u.begin(), u.end());
  reverse(u.begin(), u.end());
  long double a;
  while (u.size() > 1) {
    a = (u.at(u.size() - 1) + u.at(u.size() - 2));
    u.at(u.size() - 2) = a / 2;
    u.pop_back();
  }
  printf("%.10f", u.at(0));
}
