(define (addword word tree)
 (define (help code tree)
   (if (empty? code) (car word)
    (if (=(car code) 0)
        (if (left tree)
      (cons (help (cdr code) (left tree)) (right tree))
       +inf.0)
       (if (right tree)
      (cons (left tree) (help (cdr code) (right tree)))
       +inf.0
        ))))
  (help (cdr word) tree))
(define (left tree)
  (if (empty? tree) '()
      (if (not(pair? tree)) false
      (car tree))))
(define (right tree)
  (if (empty? tree) '()
    (if (not(pair? tree)) false
      (cdr tree))))
(define (main lst)
 (foldl addword '() lst))

(define (decode? lst)
(if (member +inf.0 (flatten (main lst))) false true))