#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 = 1; i < N - 1; i++) {
    B.at(i) = (B.at(i - 1) + A.at(i + 1)) / 2;
  }
  cout << fixed << setprecision(15) << B.at(N - 2);
}
