#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[NN-1]
  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;
}
