#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double *arr = new double[n];
  int i = 0;
  for (i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr, arr + n);
  i = 0;
  double sum = 0;
  while (n != 1) {
    i = 0;
    sum = 0;
    while (i < n) {
      sum = arr[i];
      if (i + 1 < n) {
        sum += arr[i + 1];
        arr[i] = sum / 2;
        i += 2;
      } else {
        arr[i] = sum;
        i += 1;
      }
    }
    n = i;
  }
  cout << arr[0] << endl;
  delete[] arr;
  return 0;
}
