#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);
  double max = 0;
  do {
    double temp = arr[0];
    for (int i = 1; i < n; i++) {
      temp += arr[i];
      temp /= 2;
    }
    if (temp > max) {
      max = temp;
    }
  } while (std::next_permutation(arr, arr + n));
  cout << max;
  return 0;
}
