Echo

You are given an array $A$ of length $N$, and an integer $P$. In one operation, you may pick any index $i$ with $2 \le i \le N-1$ and update both of its neighbours simultaneously: - $A_{i-1} \;\gets\; A_{i-1} \oplus A_i$ - $A_{i+1} \;\gets\; A_{i+1} \oplus A_i$ Here $\oplus$ denotes the [bitwise XOR](https://en.wikipedia.org/wiki/Bitwise_operation#XOR) operation. Note that $A_i$ itself is **not