What was a film producer that M1 and M2 starred and M3 , M4 , M5 , and M6 starred
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:film.producer .
?x0 ns:film.actor.film/ns:film.performance.film M1 .
?x0 ns:film.actor.film/ns:film.performance.film M2 .
?x0 ns:film.actor.film/ns:film.performance.film M3 .
?x0 ns:film.actor.film/ns:film.performance.film M4 .
?x0 ns:film.actor.film/ns:film.performance.film M5 .
?x0 ns:film.actor.film/ns:film.performance.film M6
}