/**

  * Definition for a binary tree node.

  * public class TreeNode {

  *     int val;

  *     TreeNode left;

  *     TreeNode right;

  *     TreeNode(int x) { val = x; }

  * }

  */

 class Solution {

     public int rangeSumBST(TreeNode root, int L, int R) {

         int result = 0;

         if (root != null) {

             if (root.val >= L && root.val <= R) {

                 result += root.val;

             }

             result += rangeSumBST(root.left, L, R);

             result += rangeSumBST(root.right, L, R);

         }

         return result;

     }

 }