Question: who was the youngest us president to die in office
[{'answer': 'John F. Kennedy', 'provenance': [{'wikipedia_id': '11262088', 'title': 'List of presidents of the United States by age', 'start_paragraph_id': 3, 'start_character': 401, 'end_paragraph_id': 3, 'end_character': 416, 'bleu_score': 1.0, 'section': 'Section::::Age of presidents.\n'}]}, {'provenance': [{'wikipedia_id': '11262088', 'title': 'List of presidents of the United States by age', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 283, 'bleu_score': 0.670984681297296, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 377512876463043684}, 'section': 'Section::::Age of presidents.\n'}]}]