(define (copy s n)
  (cond ((= n 0) '())
        (#t (cons s (copy s (- n 1))))))

(define (nest s n)
  (cond ((= n 0) '())
        ((= n 1) (cons s '()))
        (#t (cons s (cons (nest s (- n 1)) '())))))

(define (countdown n)
  (cond ((= n 1) '(1))
        (#t (cons n (countdown (- n 1))))))

(define (countup n)
  (cond ((= n 1) '(1))
        (#t (append (countup (- n 1)) (cons n '())))))