#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (n); i += (1)) {
    cin >> v[i];
  }
  double newItem;
  while (v.size() > 1) {
    sort(v.begin(), v.end(), greater<double>());
    vector<double> p;
    v.swap(p);
    while (v.size() > 1) {
      newItem = 0;
      newItem += v.back();
      v.pop_back();
      newItem += v.back();
      v.pop_back();
      newItem /= 2.0;
      v.push_back(newItem);
    }
  }
  cout << setprecision(7) << fixed << v[0];
  return 0;
}
