#include<bits/stdc++.h>
using namespace std;
double a[55];
int n;

int main()
{	cin>>n;
	for(int i=1;i<=n;++i)
		cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=2;i<=n;++i)
	{
		a[i]=(a[i-1]+a[i])/2;
		sort(a+i,a+n+1);
	}
	cout<<a[n]<<endl;
	return 0;
}