#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double> > pq;
  for (int i = 1; i <= n; ++i) {
    int temp;
    cin >> temp;
    pq.push(temp);
  }
  int ans = 0, sum = 0;
  while (pq.size() > 1) {
    sum += pq.top();
    pq.pop();
    sum += pq.top();
    pq.pop();
    pq.push(sum / 2.0);
    sum = 0;
  }
  cout << pq.top() << endl;
  return 0;
}
