#include<bits/stdc++.h>
using namespace std;

const int maxn=55;
int a[maxn],n;
double tmp;

int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;++i) scanf("%d",a+i);
	sort(a+1,a+n+1);
	tmp=a[1];
	for(int i=2;i<=n;++i) {
		tmp=(tmp+a[i])/2.0;
	}
	cout<<tmp;
}