PLSQL procedure to find the minimum of the two number

DECLARE a number; b number; c number; 

PROCEDURE findMinimum(x IN number, y IN number, z OUT number) IS
BEGIN
    IF x < y
         THEN z:= x;
    ELSE
         z:= y;
    END IF;
END; 

BEGIN
    a:= 12;
    b:= 13;
    findMinimum(a, b, c);
    dbms_output.put_line(' Minimum of (12, 13) : ' || c);
END;
/