#include <algorithm>
#include <iostream>
using namespace std;
typedef long long ll;
int main(){
	int n,i;
	cin>>n;
	double y[n],ans;
	for(i=0;i<n;i++)cin>>y[i];
	sort(y,y+n);
	ans=(y[0]+y[1])/2;
	for(i=2;i<n;i++)ans=(y[i]+ans)/2;
	cout<<ans<<endl;
}
