In this problem, there are conditional blocks. If your solution works correctly for certain constraints, it will receive a certain number of points. Note that the evaluation is still in the testing phase.

\begin{enumerate}
\item ($5$ points): $k=1$;
\item ($5$ points): $n\le 10$, $k\le 2$;
\item ($10$ points): $n\le 15$, $k\le 3$;
\item ($80$ points): without additional constraints.
\end{enumerate}