List all the collaborators of the artist which has collaborated with sanremo Music Festival?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/associatedMusicalArtist> <http://dbpedia.org/resource/Sanremo_Music_Festival> . ?x <http://dbpedia.org/ontology/associatedMusicalArtist> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Artist>}
Sanremo_Music_Festival