To how many places does the airlines fly, whose head office is located at the Gatwick Airport?
SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/ontology/headquarter> <http://dbpedia.org/resource/Gatwick_Airport> . ?x <http://dbpedia.org/property/destinations> ?uri  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Place>}
Gatwick_Airport