Did a film editor direct M2 's prequel , direct M3 's prequel , and edit M1
SELECT count(*) WHERE {
?x0 a ns:film.editor .
?x0 ns:film.director.film ?x1 .
?x0 ns:film.director.film ?x2 .
?x0 ns:film.editor.film M1 .
?x1 ns:film.film.sequel M2 .
?x2 ns:film.film.sequel M3
}