$\begin{bamtrix}1 & 0\\

0 & 1

\end{batrix}-

\begin{bmatrix}

0 & 3\\

-3 & 0

\end{bmatrix} =

\begin{bmatrix}

1 & -3

3 & 1

\end{bmatrix}$

So then what is I + S?

Let B=I+S. Then the inverse of B is

$\frac{1}{\text{det}(B)}\begin{matrix}

b_{22} & -b_{21}\\

-b_{12} & b_{11}

\end{bmatrix}$