#include<bits/stdc++.h>
using namespace std;
double a[55];
int main()
{
    int n;
    cin>>n;
    for(int i=1;i<=n;++i)
    	cin>>a[i];
	for(int i=1;i<=n;++i){
		sort(a+i,a+n+1);
		a[i+1]=(a[i+1]+a[i])/2;
	}
	cout<<a[n]<<endl;
}