B - Arithmetic Subarrays

Let's define the array $[B_1, B_2, \ldots, B_M]$ to be *good* if there exists a permutation of $[B_1, B_2, \ldots, B_M]$ that is an arithmetic progression. Formally, the array is *good* if there exist arrays $C$ and $D$ such that all of the following are satisfied: - $|C|=|D|=|B|=M$. - $C$ is a permutation of the integers from $1$ to $M$. That is, each of the numbers from $1$ to $M$ appears exa