#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; ++i) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  queue<double> ans;
  for (int i = 0; i < n; ++i) {
    ans.push(v[i]);
  }
  double x, y;
  for (int i = 0; i < n - 1; ++i) {
    x = ans.front();
    ans.pop();
    y = ans.front();
    ans.pop();
    ans.push((x + y) / 2);
  }
  cout << ans.front() << endl;
  return 0;
}
