#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double arr[n], r = 0;
  for (int i = 0; i < n; i++) cin >> arr[i];
  sort(arr, arr + n);
  r = (arr[n - 1] + arr[n - 2]) / 2;
  for (int i = n - 3; i >= 0; i--) r = (r + arr[i]) / 2;
  cout << r << '\n';
}
