$6 \rightarrow$ In a regular $n$-sided polygon, the difference between any two adjacent interior angles is $18^{\circ}$, find the maximum value of $n$,
Hedgehog, this problem can be solved in three steps:
(1) Prove that $n$ is even
(2) Prove that $n<40$, and $n \leqslant 38$;
(3) Prove that $n=38$, i.e., the maximum value of $n$ is 38.