Question: when did the berlin wall start being built
[{'answer': ') , starting on', 'provenance': [{'wikipedia_id': '3722', 'title': 'Berlin Wall', 'start_paragraph_id': 1, 'start_character': 184, 'end_paragraph_id': 1, 'end_character': 201, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3722', 'title': 'Berlin Wall', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 823, 'bleu_score': 0.6804619207583441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15420871364595422846}, 'section': 'Section::::Abstract.'}]}]