#| BEGIN (Введите свое решение) |#
(define (accumulate combiner null-value term a next b)
  (if (> a b)
    null-value
    (combiner (term a)
              (accumulate combiner
                          null-value
                          term
                          (next a)
                          next
                          b))))

(define (accumulate-iter combiner null-value term a next b)
  (define (iter a result)
    (if (> a b)
      result
      (iter (next a) (combiner result (term a)))))
  (iter a null-value))
#| END |#