Did a person play M1 and play a film that starred M3
SELECT count(*) WHERE {
?x0 a ns:people.person .
?x0 ns:film.actor.film/ns:film.performance.character ?x1 .
?x0 ns:film.actor.film/ns:film.performance.character M1 .
?x1 a ns:film.film .
?x1 ns:film.film.starring/ns:film.performance.actor M3
}