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