How many countries surround the sea into which the Upper Neratva flow?
SELECT DISTINCT COUNT(?uri) WHERE { <http://dbpedia.org/resource/Upper_Neretva> <http://dbpedia.org/ontology/riverMouth> ?x . ?x <http://dbpedia.org/ontology/country> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Sea>}
Upper_Neretva