#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;
  vector<long long> vs(n);
  for (long long i = (long long)(0); i < (long long)((n)); ++i) cin >> vs[i];
  sort(vs.begin(), vs.end(), greater<long long>());
  stack<double> s;
  for (long long i = (long long)(0); i < (long long)((n)); ++i) s.push(vs[i]);
  while (s.size() != 1) {
    long long a = s.top();
    s.pop();
    long long b = s.top();
    s.pop();
    s.push((a + b) / 2.0);
  }
  cout << s.top() << endl;
  return 0;
}
