#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, i, j, k, l, o;
  cin >> n;
  long double a[200];
  for (long long int i = 0; i <= n - 1; i++) cin >> a[i];
  sort(a, a + n);
  long double s = (a[0] + a[1]) / (1 << (n - 1));
  k = 2;
  for (long long int i = 2; i <= n - 1; i++) {
    s += ((k * (a[i])) / (1 << (n - 1)));
    k *= 2;
  }
  cout << s;
  return 0;
}
