#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  pair<int, int> p[n];
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    p[i] = (make_pair(a * 2, 2));
  }
  sort(p, p + n);
  pair<int, int> tmp = (make_pair((p[0].first + p[1].first) / 2, 2));
  for (int i = 2; i < n; i++) {
    if ((tmp.first + p[i].first) % 2 == 0) {
      tmp = (make_pair((tmp.first + p[i].first) / 2, tmp.second));
    } else {
      tmp = (make_pair((tmp.first + p[i].first), tmp.second * 2));
    }
  }
  double ans = tmp.first;
  ans = ans / tmp.second;
  cout << ans;
  return 0;
}
