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