#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  double total = 0.0;
  cin >> N;
  vector<int> vec(N);
  for (int i = 0; i < N; i++) {
    cin >> vec.at(i);
  }
  sort(vec.begin(), vec.end());
  for (int i = 0; i < N - 1; i++) {
    if (i == 0) {
      total = (vec.at(i) + vec.at(i + 1)) / 2;
    } else {
      total += (total + vec.at(i + 1)) / 2;
    }
  }
  cout << total << endl;
}
