(define (maxFrequentList l)
  (if (null? l) '()
    (maxLength (filter (lambda (x) (= (car l) x)) l) (maxFrequentList (cdr l)))))

(define (maxFrequentNum l) (car (maxFrequentList l)))

(define (mostFrequent l)
  (let ((maxFrequentInFirst (maxFrequentNum (car l))))
  (if (all? (lambda (x) (= (maxFrequentNum x) maxFrequentInFirst)) l)
      maxFrequentInFirst
      0)))