Question: when the soviet union sealed off the city of berlin
[{'answer': '1961', 'provenance': [{'wikipedia_id': '33170', 'title': 'West Berlin', 'start_paragraph_id': 3, 'start_character': 258, 'end_paragraph_id': 3, 'end_character': 262, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '33170', 'title': 'West Berlin', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 484, 'bleu_score': 0.502871669409224, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1635526083429153744}, 'section': 'Section::::Abstract.'}]}]