#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  for (auto &t : a) {
    cin >> t;
  }
  sort(a.begin(), a.end());
  double cur = (a[0] + a[1]) / 2;
  for (int i = 2; i < n; i++) {
    cur = (cur + a[i]) / 2;
  }
  cout << fixed << setprecision(15);
  cout << cur << endl;
}
