Question: what year did prince's sign of the times come out
[{'answer': 'March 31 , 1987', 'provenance': [{'wikipedia_id': '57317', 'title': 'Prince (musician)', 'start_paragraph_id': 27, 'start_character': 703, 'end_paragraph_id': 27, 'end_character': 718, 'bleu_score': 1.0, 'section': 'Section::::Career.:1987–1991: Solo again – "Sign o\' the Times", "Lovesexy", "Batman" and "Grafitti Bridge".\n'}]}, {'provenance': [{'wikipedia_id': '57317', 'title': 'Prince (musician)', 'start_paragraph_id': 27, 'start_character': 0, 'end_paragraph_id': 27, 'end_character': 717, 'bleu_score': 0.9831208473513011, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5269793187266246694}, 'section': 'Section::::Career.:1987–1991: Solo again – "Sign o\' the Times", "Lovesexy", "Batman" and "Grafitti Bridge".\n'}]}]