english: If we are able to peek inside, we might see something very complex or something very simple: $$\begin{array}{ccc} \text{input} & \mapsto & \begin{array}{|c|}\hline\text{ multiply by }3 \\ \hline\end{array} & \mapsto & \text{output }\ . \end{array}$$
non_english: うぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅぅうぐぅうぐぅぐ～ぐ～ぐ～。。。。