From how many different institutes have the members of Judge Advocate General's Corps graduated?
SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/ontology/militaryRank> <http://dbpedia.org/resource/Judge_Advocate_General's_Corps,_United_States_Army> . ?x <http://dbpedia.org/ontology/almaMater> ?uri  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/EducationalInstitution>}
Judge_Advocate_General's_Corps,_United_States_Army