|----------------------------------------------5-4-5----------0--
              b               b
 ----------------------3------------------8-7-5------------------
 -------3-5-6~-8^~-5-6---6-5-3-5^-3-------------8-7-5------------
 2~-4-5-----------------------------5-4~--------------7-6-4------
 -----------------------------------------------------------7-6-4
 ----------------------------------------------------------------
 ----------------------------------------------------------------
                                                ah
 7-5-3-------------------5-3-2----------------------|
 ------7-5-3-------------------5-3-2----------------|
 ------------6-4-2-------------------4-2-1----------|
 ------------------6-4-2-------------------4-2-1----|