#include <bits/stdc++.h>
using namespace std;
const bool DEBUG = true;
using ll = long long;
using ii = pair<int, int>;
using vi = vector<int>;
const double PI = acos(-1);
const double EPS = 1e-9;
int main() {
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  int n;
  cin >> n;
  vector<double> vs(n);
  for (int i = 0; i < n; ++i) cin >> vs[i];
  sort(vs.begin(), vs.end());
  reverse(vs.begin(), vs.end());
  swap(vs[0], vs[min(n - 1, 2)]);
  double ans = vs[0];
  for (int i = 0; i < n; ++i) ans = (ans + vs[i]) / 2.0;
  cout << ans << endl;
}
