#include <bits/stdc++.h>
using namespace std;
void quicksort(int array[], int left, int right) {
  if (left >= right) return;
  int pivot = array[right];
  int cnt = left;
  for (int i = left; i <= right; i++) {
    if (array[i] <= pivot) {
      int tmp = array[cnt];
      array[cnt] = array[i];
      array[i] = tmp;
      cnt++;
    }
  }
  quicksort(array, left, cnt - 2);
  quicksort(array, cnt, right);
}
int main() {
  int input;
  cin >> input;
  int items[input];
  for (int i = 0; i < input; i++) {
    cin >> items[i];
    for (int k = 0; k < i; k++) {
      if (items[i] == items[k]) {
        i--;
        input--;
        break;
      }
    }
  }
  quicksort(items, 0, input - 1);
  float diff = items[0];
  for (int i = 1; i < input; i++) {
    diff = (diff + items[i]) / 2;
  }
  cout << diff << endl;
  return 0;
}
