Question: how many letters are in the korean alphabet
[{'answer': '19 consonants', 'provenance': [{'wikipedia_id': '42538288', 'title': 'Hangul', 'start_paragraph_id': 43, 'start_character': 65, 'end_paragraph_id': 43, 'end_character': 78, 'bleu_score': 1.0, 'section': 'Section::::Letters.\n'}]}, {'answer': '21 vowels', 'provenance': [{'wikipedia_id': '42538288', 'title': 'Hangul', 'start_paragraph_id': 43, 'start_character': 83, 'end_paragraph_id': 43, 'end_character': 92, 'bleu_score': 1.0, 'section': 'Section::::Letters.\n'}]}, {'provenance': [{'wikipedia_id': '42538288', 'title': 'Hangul', 'start_paragraph_id': 43, 'start_character': 0, 'end_paragraph_id': 43, 'end_character': 100, 'bleu_score': 0.6470107100770991, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13958078517687826581}, 'section': 'Section::::Letters.\n'}]}]