(define (unique lst)
 (define (reverse-pair pair)
 (cons (cdr pair) (car pair)))
 (define (searching lest rez)
 (if (empty? lest) rez
 (if (or (member (car lest) rez) (member (reverse-pair (car lest)) rez)) (searching (cdr lest) rez)
 (searching (cdr lest) (cons (car lest) rez)))))
 (searching lst '()))