#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long n;
  cin >> n;
  vector<double> v;
  for (long long i = 0; i < n; i++) {
    long long y;
    cin >> y;
    v.push_back((double)y);
  }
  double x = 2.0;
  sort(v.begin(), v.end());
  vector<double>::iterator itr;
  itr = v.begin();
  while (v.size() > 1) {
    double z = (v[0] + v[1]) / x;
    v.push_back(z);
    v.erase(itr);
    v.erase(itr);
    sort(v.begin(), v.end());
  }
  cout << v[0] << endl;
  return 0;
}
