Question: when did leningrad changed back to st petersburg
[{'answer': '26 January 1924', 'provenance': [{'wikipedia_id': '24320051', 'title': 'Saint Petersburg', 'start_paragraph_id': 5, 'start_character': 385, 'end_paragraph_id': 5, 'end_character': 400, 'bleu_score': 1.0, 'section': 'Section::::Name.\n'}]}]