same-parity 2

(define (same-parity? m n)
  (= (remainder m 2)
     (remainder n 2)))

(define (same-parity fst . lst)
  (define (parity-list ls)
    (if (null? ls)
        null
        (if (same-parity? fst (car ls))
            (cons (car ls) (parity-list (cdr ls)))
            (parity-list (cdr ls)))))
  (cons fst (parity-list lst)))