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