package main

type TreeNode struct {
	Val int
	Left *TreeNode
	Right *TreeNode
}

func rangeSumBST(root *TreeNode ,low int, high int) int {
	sum := 0
	var depth func(node *TreeNode)
	depth = func(node *TreeNode) {
		if node == nil {
			return
		}
		if node.Val >= low && node.Val <= high {
			sum += node.Val
		}
		depth(node.Left)
		depth(node.Right)
	}
	depth(root)
	return sum
}