'''

def lowestCommonAncestor(self, root, p, q):

```
if not root or not p or not q:
return None
if p.val < root.val and q.val < root.val:
return self.lowestCommonAncestor(root.left, p, q)
elif p.val > root.val and q.val > root.val:
return self.lowestCommonAncestor(root.right, p, q)
return root
```