CREATE TABLE table_name_81 (total_as INTEGER, venue VARCHAR(255), team VARCHAR(255), opponent VARCHAR(255))
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"