My first stored procedure

[Chevy Mark Sunderland]

Hi all.

This is my first stored procedure create in Mysql Workbench 5.2.38 CE.

I need show the output of stored procedure and I try this but:

-- --------------------------------------------------------------------------------
-- Routine DDL
-- Note: comments before and after the routine body will not be stored by the server
-- --------------------------------------------------------------------------------
DELIMITER $$

CREATE DEFINER=`root`@`localhost` PROCEDURE `sp1`( ymstart char(6), ymstop char(6), flightspec char(2), inout result decimal(16,4) )
begin
  declare this char(6);
  set this=ymstart, result=0;
  while this <= ymstop do 
    set result = result + 
                 (select sum(my_number_of_flight_hours_e+my_number_of_flight_hours_e) 
                  from dotableone 
                  where year=left(this,4) and `month`=right(this,2) and left(my_flight_zone,2)=flightspec
                 );
    if right(this,2) >= '12' then
      set this = concat( 1+left(this,4), '01' );

    else

      set this = concat( left(this,4), if(right(this,2)<'09','0',''), 1+right(this,2) );
    end if;
  end while;
END

CALL sp1 (5, @a);
SELECT @a;

0	
16:56:05	
CALL sp1 (5, @a)	
Error Code: 1318. 
Incorrect number of arguments for PROCEDURE dbq.sp1; expected 4, got 2

Can you help me?
Many thanks