Question: what is the population of the des moines area
[{'answer': '645,911'}, {'provenance': [{'wikipedia_id': '5781274', 'title': 'Des Moines metropolitan area', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 352, 'bleu_score': 0.7464673379515631, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10088848307781325927}, 'section': 'Section::::Abstract.'}]}]