Question: who sang lead on when i'm 64
[{'answer': 'Paul McCartney', 'provenance': [{'wikipedia_id': '556635', 'title': "When I'm Sixty-Four", 'start_paragraph_id': 1, 'start_character': 81, 'end_paragraph_id': 1, 'end_character': 95, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]