#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v.at(i);
  }
  float f = v.at(0);
  sort(v.begin(), v.end());
  for (int i = 1; i < n; i++) {
    f = (f + v.at(i)) / 2.0;
  }
  cout << fixed << setprecision(15) << f << endl;
}
