Question: what was the first feature-length film to use vitaphone technology
[{'answer': 'Don Juan', 'provenance': [{'wikipedia_id': '540849', 'title': 'Vitaphone', 'start_paragraph_id': 5, 'start_character': 225, 'end_paragraph_id': 5, 'end_character': 233, 'bleu_score': 1.0, 'section': 'Section::::Early history.\n'}]}, {'provenance': [{'wikipedia_id': '540849', 'title': 'Vitaphone', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 696, 'bleu_score': 0.9373498622748081, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18191157321056528740}, 'section': 'Section::::Early history.\n'}]}]