#include <bits/stdc++.h>
using namespace std;
template <typename T>
using reversed_priority_queue =
    std::priority_queue<T, std::vector<T>, std::greater<T> >;
signed main() {
  int64_t n;
  cin >> n;
  reversed_priority_queue<double> q;
  for (int64_t i = 0; i < (n); i++) {
    int64_t x;
    cin >> x;
    q.push(x);
  }
  for (int64_t i = 0; i < (n - 1); i++) {
    int64_t x = q.top();
    q.pop();
    int64_t y = q.top();
    q.pop();
    q.push((x + y) / 2.0);
  }
  cout << q.top() << endl;
  return 0;
}
