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A cinema has `n`

rows of seats, numbered from 1 to `n`

and there are ten seats in each row, labelled from 1 to 10 as shown in the figure above.

Given the array `reservedSeats`

containing the numbers of seats already reserved, for example, `reservedSeats[i]=[3,8]`

means the seat located in row **3** and labelled with **8** is already reserved.

*Return the maximum number of four-person families you can allocate on the cinema seats.* A four-person family occupies fours seats **in one row**, that are **next to each other**. Seats across an aisle (such as [3,3] and [3,4]) are not considered to be next to each other, however, It is permissible for the four-person family to be separated by an aisle, but in that case, **exactly two people** have to sit on each side of the aisle.

**Example 1:**

Input:n = 3, reservedSeats = [[1,2],[1,3],[1,8],[2,6],[3,1],[3,10]]Output:4Explanation:The figure above shows the optimal allocation for four families, where seats mark with blue are already reserved and contiguous seats mark with orange are for one family.

**Example 2:**

Input:n = 2, reservedSeats = [[2,1],[1,8],[2,6]]Output:2

**Example 3:**

Input:n = 4, reservedSeats = [[4,3],[1,4],[4,6],[1,7]]Output:4

**Constraints:**

`1 <= n <= 10^9`

`1 <= reservedSeats.length <= min(10*n, 10^4)`

`reservedSeats[i].length == 2`

`1 <= reservedSeats[i][0] <= n`

`1 <= reservedSeats[i][1] <= 10`

- All
`reservedSeats[i]`

are distinct.