Design a system that manages the reservation state of `n`

seats that are numbered from `1`

to `n`

.

Implement the `SeatManager`

class:

`SeatManager(int n)`

Initializes a`SeatManager`

object that will manage`n`

seats numbered from`1`

to`n`

. All seats are initially available.`int reserve()`

Fetches the**smallest-numbered**unreserved seat, reserves it, and returns its number.`void unreserve(int seatNumber)`

Unreserves the seat with the given`seatNumber`

.

**Example 1:**

Input["SeatManager", "reserve", "reserve", "unreserve", "reserve", "reserve", "reserve", "reserve", "unreserve"] [[5], [], [], [2], [], [], [], [], [5]]Output[null, 1, 2, null, 2, 3, 4, 5, null]ExplanationSeatManager seatManager = new SeatManager(5); // Initializes a SeatManager with 5 seats. seatManager.reserve(); // All seats are available, so return the lowest numbered seat, which is 1. seatManager.reserve(); // The available seats are [2,3,4,5], so return the lowest of them, which is 2. seatManager.unreserve(2); // Unreserve seat 2, so now the available seats are [2,3,4,5]. seatManager.reserve(); // The available seats are [2,3,4,5], so return the lowest of them, which is 2. seatManager.reserve(); // The available seats are [3,4,5], so return the lowest of them, which is 3. seatManager.reserve(); // The available seats are [4,5], so return the lowest of them, which is 4. seatManager.reserve(); // The only available seat is seat 5, so return 5. seatManager.unreserve(5); // Unreserve seat 5, so now the available seats are [5].

**Constraints:**

`1 <= n <= 10`

^{5}`1 <= seatNumber <= n`

- For each call to
`reserve`

, it is guaranteed that there will be at least one unreserved seat. - For each call to
`unreserve`

, it is guaranteed that`seatNumber`

will be reserved. - At most
`10`

calls^{5}**in total**will be made to`reserve`

and`unreserve`

.