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

int main(){
	int n,a[52];double ans;
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	sort(a+1,a+n+1);
	ans=(a[1]+a[2])/2.0;
	for(int i=3;i<=n;i++)ans=(ans+a[i])/2.0;
	cout<<ans<<endl;
	return 0;
} 