Question: what year did russia sell alaska to the united states
[{'answer': '1867', 'provenance': [{'wikipedia_id': '193703', 'title': 'Alaska Purchase', 'start_paragraph_id': 1, 'start_character': 177, 'end_paragraph_id': 1, 'end_character': 181, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '193703', 'title': 'Alaska Purchase', 'start_paragraph_id': 1, 'start_character': 39, 'end_paragraph_id': 1, 'end_character': 275, 'bleu_score': 0.5752434330407, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11068752812268675596}, 'section': 'Section::::Abstract.'}]}]