Among all the suppliers in debt, how many of them are in Europe?
in debt refers to s_acctbal < 0; Europe refers to r_name = 'EUROPE'
SELECT COUNT(T1.n_nationkey) FROM nation AS T1 INNER JOIN region AS T2 ON T1.n_regionkey = T2.r_regionkey INNER JOIN supplier AS T3 ON T1.n_nationkey = T3.s_nationkey WHERE T2.r_name = 'EUROPE' AND T3.s_acctbal < 0