#include <bits/stdc++.h>
using namespace std;
template <typename first, typename second>
ostream &operator<<(ostream &os, const pair<first, second> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  typename vector<T>::const_iterator it;
  for (it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  return os << "}";
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &v) {
  os << "[";
  typename set<T>::const_iterator it;
  for (it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  return os << "]";
}
template <typename first, typename second>
ostream &operator<<(ostream &os, const map<first, second> &v) {
  os << "[";
  typename map<first, second>::const_iterator it;
  for (it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << it->first << " = " << it->second;
  }
  return os << "]";
}
int32_t main() {
  ios::sync_with_stdio(false);
  long long n;
  cin >> n;
  vector<long long> a(n);
  set<double> second;
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
    second.insert(1.0 * a[i]);
  }
  while (second.size() != 1) {
    auto fir = *(second.begin());
    second.erase(second.begin());
    auto sec = *(second.begin());
    second.erase(second.begin());
    auto mean = (fir + sec) / 2.0;
    second.insert(mean);
  }
  double ans = *(second.begin());
  printf("%0.9lf\n", ans);
  return 0;
}
