#include <bits/stdc++.h>

using namespace std;

int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.rbegin(), v.rend());
  for (int i = 0; i < N - 1; i++) {
    double t = v.back(); v.pop_back();
    t += v.back(); v.pop_back();
    t /= 2;
    v.push_back(t);
  }
  cout << fixed << setprecision(10) << v[0] << endl;
}