# For Solution

There is a party where `n` friends numbered from `0` to `n - 1` are attending. There is an infinite number of chairs in this party that are numbered from `0` to `infinity`. When a friend arrives at the party, they sit on the unoccupied chair with the smallest number.

• For example, if chairs `0``1`, and `5` are occupied when a friend comes, they will sit on chair number `2`.

When a friend leaves the party, their chair becomes unoccupied at the moment they leave. If another friend arrives at that same moment, they can sit in that chair.

You are given a 0-indexed 2D integer array `times` where `times[i] = [arrivali, leavingi]`, indicating the arrival and leaving times of the `ith` friend respectively, and an integer `targetFriend`. All arrival times are distinct.

Return the chair number that the friend numbered `targetFriend` will sit on.

Example 1:

```Input: times = [[1,4],[2,3],[4,6]], targetFriend = 1
Output: 1
Explanation:
- Friend 0 arrives at time 1 and sits on chair 0.
- Friend 1 arrives at time 2 and sits on chair 1.
- Friend 1 leaves at time 3 and chair 1 becomes empty.
- Friend 0 leaves at time 4 and chair 0 becomes empty.
- Friend 2 arrives at time 4 and sits on chair 0.
Since friend 1 sat on chair 1, we return 1.
```

Example 2:

```Input: times = [[3,10],[1,5],[2,6]], targetFriend = 0
Output: 2
Explanation:
- Friend 1 arrives at time 1 and sits on chair 0.
- Friend 2 arrives at time 2 and sits on chair 1.
- Friend 0 arrives at time 3 and sits on chair 2.
- Friend 1 leaves at time 5 and chair 0 becomes empty.
- Friend 2 leaves at time 6 and chair 1 becomes empty.
- Friend 0 leaves at time 10 and chair 2 becomes empty.
Since friend 0 sat on chair 2, we return 2.
```

Constraints:

• `n == times.length`
• `2 <= n <= 104`
• `times[i].length == 2`
• `1 <= arrivali < leavingi <= 105`
• `0 <= targetFriend <= n - 1`
• Each `arrivali` time is distinct.