Need Help 19th question

Can you solve it for me? I am not really getting it
\(\displaystyle S(n)=\)\(\displaystyle \left\{ \begin{gathered}
1 + i,n \equiv 0\bmod 4 \hfill \\
2i,n \equiv 1\bmod 4 \hfill \\
- 1 + i,n \equiv 2\bmod 4 \hfill \\
0,n \equiv 3\bmod 4 \hfill \\
\end{gathered} \right.\)________________ SEE HERE
 
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