#include <bits/stdc++.h>
using namespace std;
int f(int i) {
  int m = 2;
  for (int k = 1; k < i; k++) m = m * 2;
  return m;
}
int main() {
  int n, s;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  if (n == 2)
    cout << (double)(v[0] + v[1]) / 2;
  else {
    s = v[0] + v[1];
    for (int i = 2; i < n; i++) {
      s += f(i - 1) * v[i];
    }
    cout << (double)s / f(n - 1);
  }
}
