Question: who was the first elected president of south africa
[{'answer': 'Nelson Mandela', 'provenance': [{'wikipedia_id': '321700', 'title': 'President of South Africa', 'start_paragraph_id': 2, 'start_character': 384, 'end_paragraph_id': 2, 'end_character': 398, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '321700', 'title': 'President of South Africa', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 534, 'bleu_score': 0.949466006301181, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14754629551722350394}, 'section': 'Section::::Abstract.'}]}]