import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        double[] a = new double[n];

        for (int i = 0; i < n; i++) {
            a[i] = sc.nextInt();
        }

        Arrays.sort(a);

        for (int i = 1; i < n; i++) {
            a[i] = (a[i-1] + a[i]) / 2.0;
        }

        System.out.println(a[n-1]);
    }
}