Question: when was the last time the usa was debt free
[{'answer': '1835 -- 1836'}, {'provenance': [{'wikipedia_id': '5878495', 'title': 'History of the United States public debt', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 564, 'bleu_score': 0.9389730586704471, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 501393688315471245}, 'section': 'Section::::Abstract.'}]}]