#include<cstdio>
#include<algorithm>
using namespace std;
int N;
double V[55];
int main()
{
	scanf("%d",&N);
	for(int i=1;i<=N;i++)
	scanf("%lf",&V[i]);
	sort(V+1,V+N+1);
	for(int i=2;i<=N;i++)
	V[i]=(V[i-1]+V[i])/2.0;
	printf("%lf",V[N]);
	return 0;
} 