#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> v(N);
  double final_ans = 0;
  for (int i = 0; i < N; i++) {
    cin >> v.at(i);
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  for (int i = 1; i < N; i++) {
    final_ans = v.at(0);
    final_ans = (final_ans + v.at(i)) / 2;
  }
  cout << final_ans << endl;
}
