#include<bits/stdc++.h>
using namespace std;
int main(){
int n;
cin>>n;
vector<double>a(n);
for(double &x:a)cin>>x;
sort(a.begin(),a.end());
double sum=(a[0]+a[1])/2;
for(int i=2;i<n;i++){
    sum=(sum+a[i])/2;
}
cout<<sum;
return 0;
}
