#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  vector<double> vec(N);
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> vec[i];
  }
  sort(vec.begin(), vec.end());
  reverse(vec.begin(), vec.end());
  vector<double> two(N);
  two[0] = 2;
  two[N - 1] = two[N - 2];
  for (int i = 1; i < N - 1; i++) {
    two[i] = 2 * two[i - 1];
  }
  double sum = 0;
  for (int i = 0; i < N; i++) {
    sum += vec[i] / two[i];
  }
  cout << sum << endl;
}
