def inOrder(root, stack=[]):
    if root.left:
        inOrder(root.left, stack)
    stack.append(root.data)
    if root.right:
        inOrder(root.right, stack)

        
def check_binary_search_tree_(root):
    stack = []
    inOrder(root, stack)
    length = len(stack)
    for i in range(length-1):
        if stack[i] >= stack[i+1]:
            return False
    return True

flag = True
pre = -1  # As all data are >= 0 so set pre = -1


def inOrder(root):
    global flag, pre
    if root.left:
        inOrder(root.left)
    if pre < root.data:
        pre = root.data
    else:
        flag = False
        return
    if root.right:
        inOrder(root.right)


def check_binary_search_tree_(root):
    inOrder(root)
    global flag
    return flag