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