#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n];
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr, arr + n);
  float a = (arr[1] + arr[0]) / 2;
  for (int i = 2; i < n; i++) {
    a = (a + arr[i]) / 2;
  }
  cout << a;
  return 0;
}
