#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;
			double 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;
}