There are N guests $($numbered from $0$ to N$-1)$ in a sanatorium waiting to be assigned a room. In each room, any number of guests can be accommodated. However, not all guests like to have a lot of roommates.

You are given an array A of N integers: the K$-$th guest wants to be in a room that contains at most A$[$K$]$ guests, including themselves.

Write a function that, given the array A$,$ returns the minimum number of rooms needed to accommodate all guests.