import java.util.Arrays;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		
		double []v = new double[n];
		
		for(int i = 0; i < n ; i++) {
			v[i] = sc.nextDouble();
		}
		Arrays.sort(v);
		
		double ave = (v[0] + v[1])/2;
		
		for(int i = 2 ; i < n ; i++) {
			ave = (ave + v[i])/2;
		}
		System.out.println(ave);
		
		
		
	}

}
