Inserting multiple values in a function at once via a comma delimited string

Question

I want to insert multiple customers licenses into my table by using a function I create. I parse in a string separated by ,. For example:

SELECT INSERT_CUS(1, '111,222,333');

This should yield a licenses table like:

cus_id	License
1	111
1	222
1	333

CREATE TABLE customers(
    cus_id int not null
);

CREATE TABLE licenses(
    cus_id int not null, foreign key (cus_id) references customers(cus_id),
    license int not null
);

However, it errors out because I am trying to insert a string into a int column.

DELIMITER //
CREATE FUNCTION INSERT_CUS(P_CUS_ID INT, P_LICENSES VARCHAR(512))
RETURNS INT UNSIGNED
BEGIN

    INSERT INTO licenses (cus_id, license) VALUES (P_CUS_ID, P_LICENSES);
    RETURN 1;

END; //
DELIMITER ;