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