Question: who was ancient china's main enemy that lived to the north
[{'answer': 'Sui Dynasty', 'provenance': [{'wikipedia_id': '43456', 'title': 'Sui dynasty', 'start_paragraph_id': 17, 'start_character': 510, 'end_paragraph_id': 17, 'end_character': 521, 'bleu_score': 1.0, 'section': 'Section::::History.:Emperor Wen and the founding of Sui.\n'}]}, {'provenance': [{'wikipedia_id': '43456', 'title': 'Sui dynasty', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 392, 'bleu_score': 0.8093487731004061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1733339909491670358}, 'section': 'Section::::Abstract.'}]}]