def int2CAS(i):
    """Converts CAS number of a compounds from an int to an string. This is
    helpful when dealing with int CAS numbers.

    Parameters
    ----------
    CASRN : int
        CASRN [-]

    Returns
    -------
    CASRN : string
        CASRN [-]

    Notes
    -----
    Handles CAS numbers with an unspecified number of digits. Does not work on
    floats.

    Examples
    --------
    >>> int2CAS(7704349)
    '7704-34-9'
    """
    i = str(i)
    return i[:-3] + '-' + i[-3:-1] + '-' + i[-1]
