#include <iostream>
#include <algorithm>
using namespace std;

int n;
double v[55], s;

int main(){
	cin >> n;
	for (int i = 0; i < n; ++i) cin >> v[i];
	sort(v, v+n);
	s = (v[0] + v[1])/2;
	for (int i = 2; i < n; ++i){
		s = (s + v[i])/2;
	}
	cout << s;
}