Question: who has more grand slams federer or nadal
[{'answer': 'Nadal', 'provenance': [{'wikipedia_id': '17271235', 'title': 'Federer–Nadal rivalry', 'start_paragraph_id': 0, 'start_character': 8, 'end_paragraph_id': 0, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]