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