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

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    }

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

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    }

} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] a = new int[n]; a new int[n] n for(int i = 0; i < n; i++)
            a[i] = sc.nextInt(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = sc.nextInt(); a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a) Arrays.sort Arrays a long ans = a[0] + a[1]; ans a[0] + a[1] a[0] a 0 a[1] a 1 for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        } int i = 2; int i = 2; i 2 i < n i n i++ i++ i {
            ans += a[i] * Math.pow(2, i - 1);
        } {
            ans += a[i] * Math.pow(2, i - 1);
        } ans += a[i] * Math.pow(2, i - 1) ans a[i] * Math.pow(2, i - 1) a[i] a i Math.pow(2, i - 1) Math.pow Math 2 i - 1 i 1 System.out.println((double)(ans / Math.pow(2, n - 1))) System.out.println System.out System System.out (double)(ans / Math.pow(2, n - 1)) ans Math.pow(2, n - 1) Math.pow Math 2 n - 1 n 1 String[] args args public class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    }

} public class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    }

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

        Arrays.sort(a);
        long ans = a[0] + a[1];
        for(int i = 2; i < n; i++) {
            ans += a[i] * Math.pow(2, i - 1);
        }

        System.out.println((double)(ans / Math.pow(2, n - 1)));
    }

}
