\sigma^{-1} = \left(\begin{array}{ccccccc}
5 & 4 & 7 & 1 & 2 & 6 & 3
\vspace{0.5em}\\
1 & 2 & 3 & 4 & 5 & 6 & 7
\end{array}\right)=\left(\begin{array}{ccccccc}
1 & 2 & 3 & 4 & 5 & 6 & 7
\vspace{0.5em}\\
4 & 5 & 7 & 2 & 1 & 6 & 3
\end{array}\right)