(define (swap-first-two lst)
  (let ((x (cond ((null? lst) '())
                 ((null? (cdr lst)) lst)
                 (else
                  (list (car (cdr lst))
                        (car lst))))))
    (cond ((null? lst) '())
          ((null? (cdr lst)) lst)
          (else
           (append x (cdr (cdr lst)))))))



(swap-first-two '(1 2 3 4 5 6))
(swap-first-two '(1))
(swap-first-two '())

(define (bubble-up lst)
  (if (null? lst)
      '()
      (cons (if (> (car lst)
                   (car (cdr lst)))
                (car (swap-first-two lst))
                (car lst))
            (bubble-up (cdr lst)))))

(bubble-up '(4 2 1 3))