#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  multiset<double> v;
  for (int i = 0; i < (int)(n); i++) {
    double nv;
    cin >> nv;
    v.insert(nv);
  }
  for (int i = 0; i < (int)(n - 1); i++) {
    double x = 0.0;
    auto itr = v.rbegin();
    double a = *itr;
    ++itr;
    auto itr2 = itr;
    double b = *itr2;
    x = (a + b) / 2.0;
    v.erase(v.find(a));
    v.erase(v.find(b));
    v.insert(x);
  }
  auto xx = v.rbegin();
  cout << *xx << endl;
  return 0;
}
