#include <bits/stdc++.h>
using namespace std;
int n;
int a[100000];
double sum = 0;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + 1 + n);
  sum = (a[1] + a[2]) / 2;
  for (int i = 3; i <= n; i++) sum = (sum + a[i]) / 2;
  cout << sum;
}
