#include<bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin>>N;
  vector<double> A(N);
  for(int i=0;i<N;i++) cin>>A[i];
  sort(A.begin(),A.end());
  for(int k=0;k<N-1;k++){A[k+1]=(A[k]+A[k+1])/2;}
  cout<<A[N-1]<<endl;
}