#include <bits/stdc++.h>
double a[500050];
using namespace std;
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  sort(a + 1, a + 1 + n);
  long double sum = a[1] + a[2];
  int k = 2;
  for (int i = 3; i <= n; i++) {
    sum += 1.0 * k * a[i];
    k *= 2;
  }
  sum /= k * 1.0;
  cout << sum << endl;
  return 0;
}
