Question: when did the battle of york town end
[{'answer': 'October 19 , 1781', 'provenance': [{'wikipedia_id': '157770', 'title': 'Siege of Yorktown', 'start_paragraph_id': 41, 'start_character': 44, 'end_paragraph_id': 41, 'end_character': 61, 'bleu_score': 1.0, 'section': 'Section::::The siege.:British surrender.\n'}]}, {'provenance': [{'wikipedia_id': '157770', 'title': 'Siege of Yorktown', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 897, 'bleu_score': 0.9865312178338931, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13079739447819562467}, 'section': 'Section::::Abstract.'}]}]