def num_or_none(num: int) -> str:
    """
    @brief Return a number string of a number. If the number is 0 then return '-'.
    For example:
    ``` python
    >>> num_or_none(1)
    '1'
    >>> num_or_none(-5)
    '-5'
    >>> num_or_none(0)
    '-'
    ```
    """
    if num == 0:
        return "-"
    else:
        return str(num)