(define (more e)
  (define (iter acc expr)
    (match expr
      [(op s l r) (match s
                    ['+ (iter (iter (inc acc) l) r)]
                    ['* (iter (iter (dec acc) l) r)])]
      [_ acc]))
  (let ([res (iter 0 e)])
    (cond [(= res 0) "="]
          [(> res 0) "+"]
          [else "*"])))