Question: when did the ussr change its name to russia
[{'answer': '25 December 1991', 'provenance': [{'wikipedia_id': '26779', 'title': 'Soviet Union', 'start_paragraph_id': 75, 'start_character': 447, 'end_paragraph_id': 75, 'end_character': 463, 'bleu_score': 1.0, 'section': 'Section::::History.:Dissolution.\n'}]}]