#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n;
  cin >> n;
  vector<int> v;
  for (int i = 0; i < n; i++) {
    int tmp;
    cin >> tmp;
    v.push_back(tmp);
  }
  sort(v.begin(), v.end());
  double value = (v.at(0) + v.at(1)) / 2.0;
  for (int i = 2; i < n; i++) {
    value = (value + v.at(i)) / 2.0;
  }
  cout << value << endl;
  return 0;
}
