def max_oslevel(dic):
    """
    Find the maximum value of a the oslevel dictionary.

    arguments:
        dic - Dictionnary {client: oslevel}
    return:
        maximum oslevel from the dictionnary
    """
    oslevel_max = None

    for key, value in iter(dic.items()):
        if oslevel_max is None or value > oslevel_max:
            oslevel_max = value

    return oslevel_max