#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  vector<long long> vect(n, 0);
  for (int i = 0; i < n; i++) {
    cin >> vect[i];
  }
  sort(vect.begin(), vect.end());
  double sum = 0;
  long long int j = 2;
  sum = vect[0] + vect[1];
  for (int i = 2; i < n; i++) {
    sum += j * vect[i];
  }
  double k = pow(2, n - 1);
  cout << setprecision(10) << sum / k << endl;
  return 0;
}
