Question: who became leader of russia after the collapse of the soviet union
[{'answer': 'Boris Yeltsin', 'provenance': [{'wikipedia_id': '52630', 'title': 'History of Russia (1991–present)', 'start_paragraph_id': 3, 'start_character': 38, 'end_paragraph_id': 3, 'end_character': 51, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '52630', 'title': 'History of Russia (1991–present)', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 825, 'bleu_score': 0.8889972065217221, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7779132186927890209}, 'section': 'Section::::Abstract.'}]}]