oracle pl/sql procedure

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C#

create or replace

PROCEDURE CHECK_PROC
(u_username in users.username%type,p_password in users.password%type,o_roleid out users.roleid%type,o_firstname out users.firstname%type,
o_lastname out users.lastname%type,o_userid out users.userid%type)
AS 
cursor check_cur is select roleid,firstname,lastname,userid from users where username=u_username and  password=p_password;
BEGIN
open check_cur;
loop
  fetch  check_cur into o_roleid,o_firstname,o_lastname,o_userid ;
  exit when  check_cur%notfound;
   dbms_output.put_line(o_roleid ||  ''  || o_firstname ||''|| o_lastname ||''||o_userid);
   end loop;
    close check_cur;
END CHECK_PROC;

this is my procedure and while executing i am getting wrong number or types of arguments error plz plz help me out
exec check_cur('',''); this is how i am executing