Table schema:
CREATE TABLE table_name_81 (total_as INTEGER, venue VARCHAR, team VARCHAR, opponent VARCHAR)

Question: What is the sum of the total As of team bucheon sk, who had the chunnam dragons as their opponent at the bucheon venue?
SQL: SELECT SUM(total_as) FROM table_name_81 WHERE team = "bucheon sk" AND opponent = "chunnam dragons" AND venue = "bucheon"