#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-9;
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long n;
  cin >> n;
  vector<double> a(n);
  for (long long i = (0); i < ((n)); ++i) cin >> a[i];
  sort(a.begin(), a.end());
  priority_queue<double> que;
  for (long long i = (0); i < ((n)); ++i) que.push(a[i]);
  for (long long i = (0); i < ((n - 2)); ++i) {
    double tmp = 0;
    tmp += que.top();
    que.pop();
    tmp += que.top();
    que.pop();
    que.push(tmp / 2);
  }
  cout << fixed << que.top() << endl;
  return 0;
}
