Question: who was the president of the united states when the vietnam war began
[{'answer': 'Eisenhower', 'provenance': [{'wikipedia_id': '8453309', 'title': 'Role of the United States in the Vietnam War', 'start_paragraph_id': 71, 'start_character': 203, 'end_paragraph_id': 71, 'end_character': 213, 'bleu_score': 1.0, 'section': 'Section::::Under the Kennedy Administration.\n'}]}]