#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++) {
    cin >> A.at(i);
  }
  sort(A.rbegin(), A.rend());
  double ssum;
  int size;
  for (int i = 0; i < N - 1; i++) {
    size = A.size();
    ssum = (A.at(size - 1) + A.at(size - 2)) / (double)2;
    A.pop_back();
    A.pop_back();
    A.push_back(ssum);
    sort(A.rbegin(), A.rend());
  }
  cout << fixed << setprecision(6);
  cout << ssum << endl;
}
