What is the NOC code of the region of the competitors weighted 77 kg?
NOC code refers to noc; competitors weighted 77 kg refer to person_id where weight = 77;
SELECT T1.noc FROM noc_region AS T1 INNER JOIN person_region AS T2 ON T1.id = T2.region_id INNER JOIN person AS T3 ON T2.person_id = T3.id WHERE T3.weight = 77