Who is the oldest person to be elected president?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q11696', 'id': 0, 'label': 'President of the United States'}, {'type': 'INTERNAL', 'name_': 'Q4167836', 'id': 1, 'label': 'Wikimedia category'}, {'type': 'INTERNAL', 'name_': 'Q8271805', 'id': 2, 'label': 'Category:Assistants to the President of the United States'}, {'type': 'INTERNAL', 'name_': 'Q55246088', 'id': 3, 'label': 'Category:Marine One'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q1125423', 'id': 4, 'label': 'Marine One'}], 'links': [{'name_': 'P971', 'source': 2, 'target': 0, 'label': 'category combines topics'}, {'name_': 'P31', 'source': 2, 'target': 1, 'label': 'instance of'}, {'name_': 'P31', 'source': 3, 'target': 1, 'label': 'instance of'}, {'name_': 'P301', 'source': 3, 'target': 4, 'label': "category's main topic"}]}