Question: who served as pm of india for longest duration
[{'answer': 'Jawaharlal Nehru', 'provenance': [{'wikipedia_id': '844745', 'title': 'List of Prime Ministers of India', 'start_paragraph_id': 2, 'start_character': 119, 'end_paragraph_id': 2, 'end_character': 135, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '844745', 'title': 'List of Prime Ministers of India', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1178, 'bleu_score': 0.7926368233934311, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14138130279330287643}, 'section': 'Section::::Abstract.'}]}]