def get_c_option_index(args):
    """
    Get index of "-c" argument and check if it's interpreter's option
    :param args: list of arguments
    :return: index of "-c" if it's an interpreter's option and -1 if it doesn't exist or program's option
    """
    try:
        ind_c = args.index('-c')
    except ValueError:
        return -1
    else:
        for i in range(1, ind_c):
            if not args[i].startswith('-'):
                return -1
        return ind_c
