#include<iostream>

#include<queue>

using namespace std;

int main()

{

	priority_queue<double,vector<double>,greater<double> > a;

	int n,m;

	while(cin>>n)

	{

		for(int i=0;i<n;i++)

		{

			cin>>m;

			a.push(m);

		}

		for(int i=1;i<n;i++)

		{

			double temp1,temp2,temp3;

			temp1=a.top();

			a.pop();

			temp2=a.top();

			a.pop();

			temp3=(double)(temp1+temp2)/2.0;

			a.push(temp3);

		}

		cout<<a.top()<<endl;

		a.pop();

	}

	return 0;

}
