#include<bits/stdc++.h>
using namespace std;
int main(){
  int n;
  cin>>n;
  double *arr = new double[n];
  int i=0;
  for(i=0;i<n;i++){
   cin>>arr[i]; 
  }
  sort(arr,arr+n);
  i=0;
  double su=0;
  while(n!=1){
    i=0;
    sum =0;
    while(i<n){
     sum = arr[i];
      if(i+1<n){
        sum+= arr[i+1];
        arr[i] = sum/2;
        i+=2;
      }else{
        arr[i] = sum;
        i+=1;
      }
    }
    n = i;
  }
  cout<<arr[0]<<endl;
  delete []arr;
 return 0; 
}