1. Given the sequence $\left\{a_{n}\right\}\left(n \in \mathbb{R}^{*}\right)$ satisfies $a_{n}=\left\{\begin{array}{ll}n, & n=1,2,3,4,5,6, \\ -a_{n-3}, & n \geq 7, n \in \mathbb{N}^{*},\end{array}\right.$ then $a_{2023}=$ $\qquad$.
answer: -4