#include<bits/stdc++.h>
using namespace std;
int n,A[55];
int main(){
	cin>>n;
	for(int i=1;i<=n;++i)scanf("%d",&A[i]);
	sort(A+1,A+n+1);
	double ans=(A[1]+A[2])/2.0;
	for(int i=3;i<=n;++i)ans=(ans+A[i])/2.0;
	printf("%6f",ans);
	return 0;
}