Question: who determines the number of justices on the supreme court
[{'answer': 'Congress', 'provenance': [{'wikipedia_id': '24827215', 'title': 'Appointment and confirmation to the Supreme Court of the United States', 'start_paragraph_id': 15, 'start_character': 270, 'end_paragraph_id': 15, 'end_character': 278, 'bleu_score': 1.0, 'section': 'Section::::Confirmation.\n'}]}]