Who was a art director of M1 , M2 , M3 , and M4
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:people.person .
?x0 ns:film.film_art_director.films_art_directed M1 .
?x0 ns:film.film_art_director.films_art_directed M2 .
?x0 ns:film.film_art_director.films_art_directed M3 .
?x0 ns:film.film_art_director.films_art_directed M4
}