#include <bits/stdc++.h>
using namespace std;
int main() {
  std::cout << std::fixed << std::setprecision(10);
  double N;
  cin >> N;
  vector<int> num(N);
  for (int i = 0; i < N; i++) {
    cin >> num[i];
  }
  sort(num.begin(), num.end());
  double kati = 0;
  for (int i = 0; i < N - 1; i++) {
    kati = (num[i] + num[i + 1]) / 2.00000;
    num[i + 1] = kati;
  }
  cout << kati << endl;
}
