Question: how many us presidents have had a state visit to the uk
[{'answer': 'Twelve', 'provenance': [{'wikipedia_id': '50828428', 'title': 'United States presidential visits to the United Kingdom and Ireland', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 6, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '50828428', 'title': 'United States presidential visits to the United Kingdom and Ireland', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 537, 'bleu_score': 0.926517698433812, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6896954290509445833}, 'section': 'Section::::Abstract.'}]}]