(let ((un (if (cond ((null? (cons 2 '())) #f) (else (or (= 3 (car (cons 2 '()))) (number-in-set? 3 (cdr (cons 2 '())))))) (cons 1 (cons 2 '())) (cons (car (cons 3 '())) (cons 1 (cons 2 '())))))) (if (number-in-set? (car (cons 2 (cons 3 '()))) un) un (cons (car (cons 2 (cons 3 '()))) un)))