#!/usr/bin/env gosh

(define (main args)
  (let* ([A (read-num)]
         [op (read-op)]
         [B (read-num)])
    (print ((if (equal? op #\+) - +) A B)))
  0)

(define (read-op)
  (read-char))

(define (read-num)
  (define (d? c)
    (memq c (string->list "0123456789")))

  (let loop ([res '()])
    (let1 c (peek-char)
      (cond
       [(and (pair? res)
             (not (d? c)))
        (string->number (apply string (reverse! res)))]
       [else
        (read-char)
        (loop (cons c res))]))))