5. In the sequence $\left\{a_{n}\right\}$, $a_{1}=2, a_{2}=-19, a_{n+2}=\left|a_{n+1}\right|-a_{n}\left(n \in \mathbf{N}_{+}\right)$, then $a_{2019}=$
After calculation, we get $a_{1}=2, a_{2}=-19, a_{3}=17, a_{4}=36, a_{5}=19, a_{6}=-17, a_{7}=-2, a_{8}=19, a_{9}=21$, $a_{10}=2, a_{11}=-19, \cdots$, so the period of the sequence $\left\{a_{n}\right\}$ is 9. Therefore, $a_{2019}=a_{224 \times 9+3}=a_{3}=17$.