#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  float min_val, kekka, sum = 0, first, second;
  cin >> n;
  vector<float> a(n);
  vector<float>::iterator it;
  for (int i = 0; i < n; i++) cin >> a[i];
  std::vector<float>::iterator iter;
  while (2 < a.size()) {
    iter = std::min_element(a.begin(), a.end());
    first = std::distance(a.begin(), iter);
    a.erase(a.begin() + first);
    iter = std::min_element(a.begin(), a.end());
    second = std::distance(a.begin(), iter);
    a.erase(a.begin() + second);
    it = a.begin();
    it = a.insert(it, (a[first] + a[second]) / 2);
  }
  cout << (max(a[0], a[1]) + min(a[0], a[1])) / 2 << endl;
}
