#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
int main(){
    int n;
    double v[50];
    int i,j,k;
    cin>>n;
    for(i=0;i<n;i++)cin>>v[i];
    sort(v,v+n);
    for(i=1;i<n;i++)v[i]=(v[i]+v[i-1])/2.0;
    cout<<v[n-1]<<endl;
}