\left( { - 1} \right)^{I\left( {\sigma _1 } \right)} \prod\limits_{i = 1}^3 {a_{i,\sigma _1 \left( i \right)} } + \left( { - 1} \right)^{I\left( {\sigma _2 } \right)} \prod\limits_{i = 1}^3 {a_{i,\sigma _2 \left( i \right)} } + ... =