Question: who won the battle of antietam union or confederate
[{'answer': 'Union', 'provenance': [{'wikipedia_id': '84849', 'title': 'Battle of Antietam', 'start_paragraph_id': 1, 'start_character': 253, 'end_paragraph_id': 1, 'end_character': 258, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]