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