#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> math(N);
  for (int i = 0; i < N; i++) {
    cin >> math.at(i);
  }
  for (int i = 0; i < N; i++) {
    for (int j = i + 1; j < N; j++) {
      if (math.at(i) < math.at(j)) {
        swap(math.at(i), math.at(j));
      }
    }
  }
  double q = (math.at(N - 1) + math.at(N - 2)) / 2;
  if (N > 2) {
    for (int i = N - 3; i >= 0; i--) {
      q = (q + math.at(i)) / 2.0;
    }
  }
  cout << q << endl;
}
