#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const long long INF = 1e9 + 47;
const long long LINF = INF * INF;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n;
  cin >> n;
  set<double> s;
  for (int i = (0); i < (n); ++i) {
    int x;
    cin >> x;
    s.insert(x);
  }
  while ((int)((s).size()) > 1) {
    auto l = *s.begin();
    s.erase(s.begin());
    auto p = *s.begin();
    s.erase(s.begin());
    s.insert((l + p) / 2.0);
  }
  cout << *s.begin() << endl;
  cerr << "Time elapsed: " << clock() / (double)CLOCKS_PER_SEC << endl;
  return 0;
}
