Question: who has won the most leading actor oscars
[{'answer': 'Katharine Hepburn', 'provenance': [{'wikipedia_id': '18739638', 'title': 'List of actors with two or more Academy Awards in acting categories', 'start_paragraph_id': 2, 'start_character': 89, 'end_paragraph_id': 2, 'end_character': 106, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]