Question: who won the last triple crown before justify
[{'answer': 'American Pharoah', 'provenance': [{'wikipedia_id': '19116721', 'title': 'Triple Crown of Thoroughbred Racing (United States)', 'start_paragraph_id': 3, 'start_character': 274, 'end_paragraph_id': 3, 'end_character': 290, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19116721', 'title': 'Triple Crown of Thoroughbred Racing (United States)', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 400, 'bleu_score': 0.96746874041754, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16530363866143295006}, 'section': 'Section::::Abstract.'}]}]