#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> val(n);
  for (int(i) = 0; (i) < (n); ++(i)) cin >> val[i];
  double x = 0;
  double y = 0;
  for (int i = 0; i < n; ++i) {
    sort(val.rbegin(), val.rend());
    x = val.back();
    val.pop_back();
    y = val.back();
    val.pop_back();
    val.push_back((x + y) / 2);
  }
  cout << val[0] << endl;
}
