def mk_ref_id(refname: str) -> str:
    """Create gerrit CD/ABCD name, refname must not be empty.

    >>> mk_ref_id("1")
    '01/1'
    >>> mk_ref_id("41242")
    '42/41242'
    """
    refid = refname[-2:] if len(refname) > 1 else ("0" + refname[-1])
    return refid + "/" + refname