public static int SumTree(SumTheTreeNode root)
        {
            if (root == null)
            {
                return(0);
            }

            int sum = root.Value;

            sum += SumTree(root.Left);
            sum += SumTree(root.Right);

            return(sum);
        }
 public SumTheTreeNode(int value, SumTheTreeNode left = null, SumTheTreeNode right = null)
 {
     Value = value;
     Left  = left;
     Right = right;
 }
 public int Test(SumTheTreeNode root) =>
 Kata.SumTree(root);