#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    int n;
    cin>>n;
    
    int v[n];
    for (int i=0; i<n; i++){
        cin>>v[i];
        
    }
    sort(v.begin(),v.end());
    double ans;
    ans=(v[0]+v[1])/2;
    
    for(int i=3;i<n;i++){
        ans=(ans+v[i])/2;
    }
    cout<<ans<<endl;
    
    
    
    return 0;
}