Alyssa’s reading club has a list of $18$ novels that they hope to read over the course of the next year. Of these novels, $13$ are in the mystery genre, $15$ are in the science fiction genre, and $8$ are in the comedy genre. $1$ book is both science fiction and comedy but not mystery and another $1$ book is both comedy and mystery but not science fiction. $6$ of the books are in all $3$ genres.
How many novels are both in the mystery and science fiction genre, but not in the comedy genre?