Chef and Good Array

Chef comes across a very interesting problem. He has an array $A$ of length $N$, and his task is to **delete** some elements from the array to make the array *good*. An array is termed *good* if: - The length of the array is **even**; - Let the length of the array $A$ after some (possibly zero) deletions be $M$, where $M$ is even. Then, $A_1+A_2 = A_3 + A_4 = \ldots = A_{M-1} + A_M$ should ho