Write a lisp program to check whether a binary tree is a Binary Search Tree. A Binary Search Tree (BST) is a tree in which all the nodes follow the below-mentioned properties: The left sub-tree of a node has a key less than or equal to its parent node's key. The right sub-tree of a node has a key greater than to its parent node's key. Example of a binary search tree A list can be used to represent the structure of a binary tree as follow: '18 (3 (1 () ()) (6 (4 () ())( 7 () ()))) (10 (()) (14 (13) ())))