Question: what was the number one song on august 31st 2017
[{'answer': 'Despacito', 'provenance': [{'wikipedia_id': '52615934', 'title': 'List of Billboard Hot 100 number-one singles of 2017', 'start_paragraph_id': 2, 'start_character': 524, 'end_paragraph_id': 2, 'end_character': 533, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]