Given a binary search tree (BST) where all node values are unique, and two nodes from the tree p and q, return the lowest common ancestor (LCA) of the two nodes.

The lowest common ancestor between two nodes p and q is the lowest node in a tree T such that both p and q are descendants. The ancestor is allowed to be a descendant of itself.

Example 1:

Input: root = [5,3,8,1,4,7,9,null,2], p = 3, q = 8

Output: 5

Example 2:

Input: root = [5,3,8,1,4,7,9,null,2], p = 3, q = 4

Output: 3

Explanation: The LCA of nodes 3 and 4 is 3, since a node can be a descendant of itself.

Constraints:

• 2 <= The number of nodes in the tree <= 100.
• -100 <= Node.val <= 100
• p != q
• p and q will both exist in the BST.