#include <bits/stdc++.h>
#include <iomanip>
using namespace std;

int c(){
    int n;
    cin >> n;
    vector<double> v(n);
    while( n>0){
        int t;
        cin >> t;
        v.at(n-1) = t;
        n--;
    }
    std::sort(v.begin(),v.end());
    double m=0;
    for( auto e = v.begin(); e!= v.end(); ++e){
        if( e==v.begin())
            m = *e;
        else
            m = (m + *e)/2.0;
    }
    cout << fixed << setprecision(10) << m << endl;

    return 0;
}