Let L$1,$ L$2,$ L$3$ be languages over the alphabet $\{$a$,$ b$,$ c$,$ d$\}$ and let L denote the

complement of a language L$.$ If

$$ L$1$ L$2=$ L$3$ and

$$ L$3$ is not regular,

then what, if anything, can you say about the languages L$1$ and L$2?$ Explain your answer.