#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 0; i < n - 1; i++)
    for (int j = 1; j < n; j++) {
      if (a[i] > a[j]) {
        float t;
        t = a[i];
        a[i] = a[j];
        a[j] = t;
      }
    }
  int k = 0;
  int l = 1;
  while (k < n - 1) {
    a[l] = (a[k] + a[l]) / 2.0;
    k++;
    l++;
  }
  cout << a[n - 1];
}
