import java.util.ArrayList;
import java.util.Collections;

public class CheckForBST {

  // function to find out the inorder traversal of the tree.
	private static void inOrder(BinaryTreeNode root, ArrayList<Integer> list){
		if(root == null)
			return;
		inOrder(root.left, list);
		list.add(root.data);
		inOrder(root.right, list);
	}

	// function to find out the inorder traversal of the tree.
	private static boolean isBST(BinaryTreeNode root){
		ArrayList<Integer> list = new ArrayList<>();
		inOrder(root, list);

    // In java you can check if the arrayList is sorted or not in foll way.
		ArrayList<Integer> sortedList = (ArrayList<Integer>) list.clone();
		Collections.sort(sortedList);

		return list.equals(sortedList);
	}

	public static void main(String[] args) {
    // Line -32,33 is just to take input of binary tree from user. You can use your own method to take input for the same.
		BSTUseBetterApproach obj = new BSTUseBetterApproach();
		BinaryTreeNode root = obj.getTreeDetailsByLevelOrder();

    // Call to isBST function with passing rootNode of the tree as argument.
		String result = isBST(root)?"BST":"Not BST";

		System.out.println(result);
	}
}