How many Japanese suppliers have their accounts in debt?
Japanese refers to n_name = 'Japan'; have accounts in debt refers to s_acctbal < 0
SELECT COUNT(T1.s_suppkey) FROM supplier AS T1 INNER JOIN nation AS T2 ON T1.s_nationkey = T2.n_nationkey WHERE T1.s_acctbal < 0 AND T2.n_name = 'JAPAN'