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

int main()
{
  	int n;
    double ans;
  	vector<double> v;
  
  	cin >> n;
  	for(int i = 0; i < n; i++) cin >> v[i]
	sort(v);
  	ans = (v[0]+v[1])/2.0;
  	for(int i = 2; i < n; i++)
    {
      ans = (ans+v[1])/2.0;
    }
  	cout << ans << endl;
}
