#include <bits/stdc++.h>
using namespace std;

int main(){
  int N;
  double total=0.0;
  vector<int> vec:
  cin >> N;
  for(int i=0;i<N;i++){
    cin >> vec.at(i);
  }
  sort(vec.begin(),vec.end());
  for(int i=0;i<N-1;i++){
    if(i == 0){
      total = (vec.at(i) + vec.at(i+1)) / 2;
    }else{
      total += (total + vec.at(i+1)) / 2;
    }
  }
  cout << total << endl;
}  
    