How many {student of} are for {Caspar David Friedrich} ?
Who were the students of Caspar David Friedrich?
SELECT (COUNT(?obj) AS ?value ) { wd:Q104884 wdt:P1066 ?obj }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q104884> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1066> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

Who were Caspar David Friedrich's students?