Joining Date

$N$ candidates (numbered from $1$ to $N$) join Chef's firm. The first $5$ candidates join on the first day, and then, on every subsequent day, the next $5$ candidates join in. For example, if there are $12$ candidates, candidates numbered $1$ to $5$ will join on day $1$, candidates numbered $6$ to $10$ on day $2$ and the remaining $2$ candidates will join on day $3$. Candidate numbered $K$ deci