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

priority_queue<double> que;

int main() {
	int n;
	cin >> n;
	double num;
	for(int i =1 ; i <= n ; i++ ){
		cin >> num ;
		que.push(-num);
	}
	while(que.size() > 1){
		double avg ;
		double t = que.top();
		que.pop();
		t += que.top();
		que.pop();
		avg = t/2.0;
		que.push(avg);
	}
	cout << -que.top() << endl;
	return 0;
}