#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double ans, x, y;
  cin >> n;
  vector<double> v(n, 0);
  for (int(i) = 0; i < (n); i++) cin >> v.at(i);
  sort(v.begin(), v.end());
  for (int(i) = 0; i < (n - 1); i++) v.at(i + 1) = (v.at(i) + v.at(i + 1)) / 2;
  ans = v.at(n - 2);
  cout << ans << endl;
}
