-----------------------------------------------------|
-----------------------------------------------------|
--------------------2------------2-------------------|
--------2----4-----------4-4-2-4---------------------|
-2-3-4-----------------------------------------------|
-----------------------------------------------------|
then
----------------------------------------------|
----------------------------------------------|
---------------2------------------------------|
-----2----4--------4---2----------------------|
-234----------------------4----2--------------|
-----------------------------------1----------|
opening
---------------------------------|
---------------------------------|
---------------------------------|
-4-------------------------------|
-2---232323232323232--------4----|
----------------------3---3------|