Question: what is the minimum number of fleet master chiefs
[{'answer': 'four', 'provenance': [{'wikipedia_id': '524652', 'title': 'Master chief petty officer', 'start_paragraph_id': 29, 'start_character': 176, 'end_paragraph_id': 29, 'end_character': 180, 'bleu_score': 1.0, 'section': 'Section::::Advancement.:Fleet and force master chief petty officer.\n'}]}, {'provenance': [{'wikipedia_id': '524652', 'title': 'Master chief petty officer', 'start_paragraph_id': 29, 'start_character': 0, 'end_paragraph_id': 29, 'end_character': 221, 'bleu_score': 0.9466178497997021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4899973247461696627}, 'section': 'Section::::Advancement.:Fleet and force master chief petty officer.\n'}]}]