#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const double epsilon = 1e-9;
const int maxn = 1e6 + 10;
void solve() {
  long long int n;
  cin >> n;
  multiset<double> v;
  for (int i = 0; i < n; i++) {
    double el;
    cin >> el;
    v.insert(el);
  }
  while (v.size() > 1) {
    double e1 = *v.begin(), e2 = *(++v.begin());
    v.erase(e1);
    v.erase(e2);
    v.insert((e1 + e2) * 0.5);
  }
  cout << fixed;
  cout << setprecision(6) << *v.begin();
}
int main() {
  int t = 1;
  while (t--) solve();
  cerr << "Time elapsed: " << clock() / (double)CLOCKS_PER_SEC << endl;
  return 0;
}
