#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-9;
signed main() {
  ios::sync_with_stdio(false);
  cout.tie(0);
  cout.precision(20);
  long long n;
  cin >> n;
  multiset<double> vs;
  for (long long i = (long long)(0); i < (long long)((n)); ++i) {
    long long v;
    cin >> v;
    vs.insert(v);
  }
  while (vs.size() != 1) {
    long long a = *vs.begin();
    vs.erase(vs.begin());
    long long b = *vs.begin();
    vs.erase(vs.begin());
    vs.insert((a + b) / 2.0);
  }
  cout << *vs.begin() << endl;
  return 0;
}
