____4_____opt.
____6_____4
____5_____2
____6_____3
____4_____1
__________x
____1_____1
____1_____1
____1_____1
____3_____3
____4_____4
__________x
__________x
____9_____3
____10____4
____10____3
__________x
____9_____1
__________
____13____4
____10____2
__________x
____11____3
____9_____1
____13____3
____13____3
____13____3
____11____1
__________x
__________x
____8_____1
____9_____2
____10____3
____11____4
__________x
__________x
