#include <bits/stdc++.h>

using namespace std;


int main(void)
{
    int N;
    cin >> N;
    vector<int> v(N);
    double ans = 0;
    for(int i = 0; i<N; i++)
    {
        cin >> v.at(i);
    }
    sort(v.begin(),v.end());
    ans = (V.at(0) + v.at(1))/2.0;
    int i = 2
    while(i<N)
    {
        ans = (ans + v.at(i))/2.0;
        i++;
    }
    
    cout << ans << endl;

}    