(define (read-zero foo)
  (cond
    ((> foo 99) (display foo))
    ((> foo 9) (begin (display 0) (display foo)))
    (else (begin (display 0) (display 0) (display foo)))
  )
)

(let loop((foo  000))
  (begin
    (read-zero foo)
    (newline)
    (when (string=? (read) "unlocked")
      (loop (+ foo 1))
    )
  )
)