#include<bits/stdc++.h>
using namespace std;
int main()
{
  int n;
   
  vector<float>vect;
 cin>>n;
 
 for(int i=0;i<n;i++)
 { 
  float y;
   cin>>y;
  vect.push_back(y);
 }
  sort(vect.begin(),vect.end());
 while(vect.size()!=1)
 {
     sort(vect.begin(),vect.end());
   float x=vect[0];
   float y=vect[1];
   vect.push_back((float)(x+y)/2);
   vect.pop_front();
   vect.pop_front();
 }
  cout<<vect.front()<<endl;
  return 0;
}