#include <iostream>
using namespace std;

int main(){
  int n;
  cin >> n;
  vector<long double> V(n);
  for (int i = 0; i < n; ++i){
  	cin >> V[i];
  }
  sort(V.begin(), V.end());
  long double factor = 2;
  long double max = V[n-1]/2;
  for (int i = n - 2; i >= 0; --i){
  	if (i != 0) factor *= 2;
    max += V[i]/factor;
  }
  cout << max;
}