read-nums
m:
    save-a
    "/"
    swap
    45
    ljust
    "\\"
    @1
    @2
    rjust
    catenate #(list+list)
    ( "\xe2\x97\x87" )
    pair
    push-a
    dec
    not
    get
    show-line
    @3
    rrange
    m:
        inc
        "\\"
        over
        ljust
        push-a
        rjust
        "/"
        rot
        rjust
        show-line