class Solution {
public:
    int rangeSumBST(TreeNode* root, int L, int R) {
        int sum = 0;
        if(!root){
            return sum;
        }
        if(L <= root->val && R >= root->val){
            sum += root->val;
        }
        if(L < root->val){
            sum += rangeSumBST(root->left,L,R);
        }
        if(R > root->val){
            sum += rangeSumBST(root->right,L,R);
        }
        return sum;
    }
};