Give a context-free description for the set of words of the form $w_1aw_2aw_3$ such that $w_1,w_2,w_3$ are constructed over the alphabet $\{0,1\}$, the sizes of $w_1$ and $w_3$ coincide, $w_1w_3$ represent a multiple of $12$ in binary (in particular, the empty word represents $0$, which is multiple of $12$), and $w_2$ is a sequence of $0$’s followed by a sequence of $1$’s where the number $0$’s and $1$’s coincide.