#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n;
  cin >> n;
  double arr[n];
  for (int i = 0; i < n; i++) cin >> arr[i];
  sort(arr, arr + n);
  double ans = (arr[0] + arr[1]) / 2;
  for (int i = 3; i < n; i++) ans = (ans + arr[i]) / 2;
  cout << ans << endl;
  return 0;
}
