I\left( {\sigma _1 } \right) = 0,I\left( {\sigma _2 } \right) = 1,I\left( {\sigma _3 } \right) = 1,I\left( {\sigma _4 } \right) = 2,I\left( {\sigma _5 } \right) = 2,I\left( {\sigma _6 } \right) = 3