I-----------------------------------------------------------------------| II
I-----------------------------------------------------------------------| II
I--------------------------------(b9)--(b9)(b9)---7----7----7(b9)--------------|OII
I--------------------------------(b9)--(b9)(b9)---7----7----7(b9)--------------| II
I---------5--7--------10----(b9)---7---7-7----5-X--5-X--5/7---------------|OII
I---5--7---------0------------------------------------------------------| II

Do that a few times....then

I---------------------------II----------------------------------------|
I---------------------------II----------------------------------------|
I---2----------------2.----OII---2-----4--4--4--4--4--4--4------------|
I---2----------------2.-----II---2-----4--4--4--4--4--4--4------------|
I---0----------------0.----OII---0-----2--2--2--2--2--2--2------------|
I---------------------------II----------------------------------------|