Was a Mexican person that edited M1 and M2 M3 's writer
SELECT count(*) WHERE {
?x0 a ns:people.person .
?x0 ns:film.editor.film M1 .
?x0 ns:film.editor.film M2 .
?x0 ns:film.writer.film M3 .
?x0 ns:people.person.nationality ns:m.0b90_r
}