What art director did M1 employ , M2 employ , and M3 's employer employ
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:film.film_art_director .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company ?x1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
?x1 ns:business.employer.employees/ns:business.employment_tenure.person M3
}