#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ;
  int n;
  cin >> n;
  vector<int> a(n);
  for (auto& x : a) cin >> x;
  double ans = 0.0;
  sort(a.rbegin(), a.rend());
  while (a.size() >= 2) {
    ans = a.back() + a[a.size() - 2];
    ans /= 2.0;
    a.pop_back();
    a.pop_back();
    a.push_back(ans);
  }
  cout << fixed << setprecision(10) << ans << '\n';
  return 0;
}
