#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  set<double> a;
  for (long long i = 0; i < n; i++) {
    double x;
    cin >> x;
    a.insert(x);
  }
  if ((long long)a.size() == 1) {
    cout << *a.begin() << "\n";
    return 0;
  }
  while ((long long)a.size() > 1) {
    auto it = a.begin();
    double f = *it;
    a.erase(it);
    it = a.begin();
    double s = *it;
    a.erase(it);
    double m = (f + s) / 2;
    a.insert(m);
  }
  cout << *a.begin() << "\n";
  return 0;
}
