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