#include <bits/stdc++.h>
using namespace std;
long long a[100];
long long gcd(long long a, long long b) { return !b ? a : gcd(b, a % b); }
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (long long i = 2; i < n; i++) a[i] = a[i] << (i - 1);
  long long s = 0;
  for (int i = 0; i < n; i++) s = s + a[i];
  long long t = (1 << (n - 1));
  long long g = gcd(s, (1 << (n - 1)));
  s /= g;
  t /= g;
  double ans = s / t + (double)(s % t) / t;
  printf("%lf", ans);
  return 0;
}
