Question: which u.s. president authorized the wearing of green berets by u.s. army special forces soldiers
[{'answer': 'President John F. Kennedy', 'provenance': [{'wikipedia_id': '25921355', 'title': 'Berets of the United States Army', 'start_paragraph_id': 25, 'start_character': 67, 'end_paragraph_id': 25, 'end_character': 92, 'bleu_score': 1.0, 'section': 'Section::::Green.\n'}]}, {'provenance': [{'wikipedia_id': '25921355', 'title': 'Berets of the United States Army', 'start_paragraph_id': 25, 'start_character': 0, 'end_paragraph_id': 25, 'end_character': 826, 'bleu_score': 0.9864398934896761, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5862593409825973127}, 'section': 'Section::::Green.\n'}]}]