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