#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v;
  for (int i = 0; i < (int)(n); i++) {
    double nv;
    cin >> nv;
    v.push_back(nv);
  }
  sort(v.begin(), v.end(), greater<double>());
  for (int i = 0; i < (int)(n - 1); i++) {
    sort(v.begin(), v.end(), greater<double>());
    double x = (v[0] + v[1]) / 2.0;
    v.push_back(x);
    v.erase(v.begin(), v.begin() + 1);
  }
  cout << v[0] << endl;
  return 0;
}
