#include <bits/stdc++.h>
using namespace std;
int main() {
  size_t n;
  cin >> n;
  vector<int> v(n);
  for (size_t i = 0; i < n; ++i) cin >> v[i];
  sort(v.begin(), v.end());
  double value = .0;
  for (size_t i = 0; i < n; ++i) {
    size_t index = (i == 0) ? n - 2 : n - i - 1;
    value += static_cast<double>(v[i]) / static_cast<double>(2 << index);
  }
  cout << fixed << setprecision(5) << value << endl;
  return EXIT_SUCCESS;
}
