#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  double total = 0.0;
  vector<int> vec;
  cin >> N;
  if (N != 0) {
    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;
  }
}
