#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
const ll oo = 0x3f3f3f3f3f3f3f3fLL;
const double eps = 1e-9;
int main() {
  ios::sync_with_stdio(false);
  ll n;
  cin >> n;
  multiset<double> blob;
  for (ll i = (0); i < (n); i++) {
    ll a;
    cin >> a;
    blob.insert(a);
  }
  while (blob.size() > 1) {
    double firs = *blob.begin();
    blob.erase(firs);
    double secon = *blob.begin();
    blob.erase(secon);
    blob.insert((firs + secon) / 2.0);
  }
  cout << *blob.begin() << endl;
}
