MySQL CREATE FUNCTION Syntax

I am trying to create a function in MySQL:

Here is the SQL code:

CREATE FUNCTION F_Dist3D (x1 decimal, y1 decimal) 
RETURNS decimal
DETERMINISTIC
BEGIN 
 DECLARE dist decimal;
 SET dist = SQRT(x1 - y1);
 RETURN dist;
END;

I am getting the following error:

#1064 - You have an error in your SQL syntax; 
check the manual that corresponds to your MySQL 
server version for the right syntax to use near '' at line 10

I am running this create statement in phpMyAdmin. What is wrong with this function?