#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  vector<double> v(n);
  for (long long(i) = 0; (i) < (n); (i)++) cin >> v[i];
  sort(v.begin(), v.end());
  while (v.size() > 1) {
    vector<double> u;
    for (int i = 0; i < (long long)v.size(); i += 2) {
      double tmp = v[i];
      if (i != (long long)v.size() - 1) {
        tmp += v[i + 1];
        tmp /= 2.0;
      }
      u.push_back(tmp);
    }
    sort(u.begin(), u.end());
    v = u;
  }
  cout << v[0] << endl;
  return 0;
}
