Question: how many grand slam matches has nadal won
[{'answer': '17', 'provenance': [{'wikipedia_id': '22825058', 'title': 'Rafael Nadal career statistics', 'start_paragraph_id': 1, 'start_character': 554, 'end_paragraph_id': 1, 'end_character': 556, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '22825058', 'title': 'Rafael Nadal career statistics', 'start_paragraph_id': 14, 'start_character': 0, 'end_paragraph_id': 14, 'end_character': 410, 'bleu_score': 0.7442611797110911, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9371274651239705536}, 'section': 'Section::::Grand Slam tournament finals.:Singles: 26 (18 titles, 8 runner-ups).\n'}]}]