What is the {human} for {secretary general} of {Social Democratic Party of Germany}
Who is the person as secretary general of Social Democratic Party of Germany?
 select distinct ?obj where { wd:Q49768 wdt:P3975 ?obj . ?obj wdt:P31 wd:Q5 } 
select distinct ?obj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q49768> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P3975> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj . ?obj <http://www.wikidata.org/entity/P31> <http://wikidata.dbpedia.org/resource/Q5> } 
Give me the name of the person secretary general of the Social Democratic Party of Germany.