#include<cstdio>
#include<algorithm>
using namespace std;
int n,i;
double ans,a[55];
int main()
{
	scanf("%d",&n);
	for (i=1;i<=n;i++)
	scanf("%lf",&a[i]);
	sort(a+1,a+n+1);
	for (ans=a[1],i=2;i<=n;i++)
	ans=(ans+a[i])/2;
	printf("%lf\n",ans);
	return 0;
}