modify length Chap09 p162 L4
add olength0 Chap09 p162 L6
add olength<=1 Chap09 p163 L2
modify olength<=1 Chap09 p163 L3
add olength<=2 Chap09 p164 L1
modify length0 Chap09 p165 L3
modify length<=1 Chap09 p165 L4
modify length<=2 Chap09 p166 L1
modidy length0 Chap09 p166 L5
modify length<=1 Chap09 p167 L1 (left)
modify length<=2 Chap09 p167 L1 (right)
add length<=3 Chap09 p167 L2
modify length0 Chap09 p168 L3 (left)
modify length0 Chap09 p168 L3 (rigth)
modify length<=1 Chap09 p169 L1
modify olength Chap09 p169 L4
modify olength Chap09 p170 L4
revert olength Chap09 p173 L1
modify olength Chap09 p173 L4
modify olength Chap09 p174 L1