# Definition for a binary tree node.

class TreeNode(object):

def __init__(self, x):

self.val = x

self.left = None

self.right = None

class Solution(object):

def rangeSumBST(self, root, L, R):

"""

:type root: TreeNode

:type L: int

:type R: int

:rtype: int

"""

# if not root:

# return 0

# elif root.val in range(L, R + 1):

# return root.val + self.rangeSumBST(root.left, L, R) + self.rangeSumBST(root.right, L, R)

# elif root.val < L:

# return self.rangeSumBST(root.right, L, R)

# else:

# return self.rangeSumBST(root.left, L, R)

if not root:

return 0

ans = 0

stack = [root]

while len(stack) > 0:

p = stack.pop()

if p.val >= L and p.val <= R:

ans += p.val

if p.left is not None:

stack.append(p.left)

if p.right is not None:

stack.append(p.right)

return ans