using System;

public class Program

{

    public class TreeNode

    {

        public int val;

        public TreeNode left;

        public TreeNode right;

        public TreeNode(int val, TreeNode left = null, TreeNode right = null)

        {

            this.val = val;

            this.left = left;

            this.right = right;

        }

    }

    public static double MaxAverage;

    public static double GetMaxAverageSubtree(TreeNode root) 

    {

        MaxAverage = 0;    

        DFS(root);

        return MaxAverage;

    }

    public static int[] DFS(TreeNode node) 

    {

        if (node == null) 

            return new int[] { 0, 0 };

        int[] left = DFS(node.left);

        int[] right = DFS(node.right);

        int num = 1 + left[0] + right[0];

        int sum = node.val + left[1] + right[1];

        MaxAverage = Math.Max(MaxAverage, (double)sum / (double)num);

        return new int[] { num, sum };

    }

    public static void Main()

    {

        Console.WriteLine("UniLecs");

        // tests

        var root = new TreeNode(5);

        root.left = new TreeNode(6);

        root.right = new TreeNode(1);

        Console.WriteLine(GetMaxAverageSubtree(root)); // 6.0

    }

}