#| BEGIN (Write your solution here) |#
(define (adjoin-set x s)
    (define (insert left x right)
        (cond
            ((null? right) (append left (list x)))
            ((= x (car right)) (append left right))
            ((< x (car right)) (append left (list x) right))
            (else (insert (append left (list (car right))) x (cdr right)))
        )
    )
    (insert '() x s)
)
#| END |#