Did M3 star a art director that M1 starred and M2 starred
SELECT count(*) WHERE {
?x0 a ns:film.film_art_director .
?x0 ns:film.actor.film/ns:film.performance.film M1 .
?x0 ns:film.actor.film/ns:film.performance.film M2 .
M3 ns:film.film.starring/ns:film.performance.actor ?x0
}