function is in an invalid state

SQL code

create or replace function city2region(quxian_id number)
return number
as 
v_id number;
begin 
 select region_id into v_id from region where city_id = quxian_id;
 return v_id
 end

select quxianchadishi(123) from dual,jiu 报错了，请问怎么回事啊？

------解决方案--------------------
函数有语法错误！
------解决方案--------------------
仔细看看，就能发现错误，呵呵