#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 k = 0;
  for (int i = 0; i < n - 1; i++) {
    k = (arr[i] + arr[i + 1]) / 2.0;
    arr[i + 1] = k;
  }
  cout << k << endl;
}
