Was a character employed by M1 , employed by M2 , and employed by M3
SELECT count(*) WHERE {
?x0 a ns:fictional_universe.fictional_character .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M3
}