Question: what is the first 16 bits of an ipv6 6to4 address
[{'answer': '2002 :', 'provenance': [{'wikipedia_id': '683274', 'title': '6to4', 'start_paragraph_id': 15, 'start_character': 103, 'end_paragraph_id': 15, 'end_character': 108, 'bleu_score': 1.0, 'section': 'Section::::How 6to4 works.:Address block allocation.\n'}]}, {'provenance': [{'wikipedia_id': '683274', 'title': '6to4', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 810, 'bleu_score': 0.951970822989707, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13807713935093253994}, 'section': 'Section::::Abstract.'}]}]