New Year's Puzzle

Description:

Input:

The first line contains an integer $$$t$$$ ($$$1 \leq t \leq 10^4$$$) — the number of test cases. Then $$$t$$$ test cases follow.

Each test case is preceded by an empty line.

The first line of each test case contains two integers $$$n$$$ and $$$m$$$ ($$$1 \le n \le 10^9$$$, $$$1 \le m \le 2 \cdot 10^5$$$) — the length of the strip and the number of blocked cells on it.

Each of the next $$$m$$$ lines contains two integers $$$r_i, c_i$$$ ($$$1 \le r_i \le 2, 1 \le c_i \le n$$$) — numbers of rows and columns of blocked cells. It is guaranteed that all blocked cells are different, i.e. $$$(r_i, c_i) \ne (r_j, c_j), i \ne j$$$.

It is guaranteed that the sum of $$$m$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.

Output:

For each test case, print on a separate line:

• "YES", if it is possible to tile all unblocked squares with the $$$2 \times 1$$$ and $$$1 \times 2$$$ tiles;
• "NO" otherwise.

You can output "YES" and "NO" in any case (for example, the strings yEs, yes, Yes and YES will be recognized as positive).

Sample Input:

3

5 2
2 2
1 4

3 2
2 1
2 3

6 4
2 1
2 3
2 4
2 6

Sample Output:

YES
NO
NO

Note:

The first two test cases are explained in the statement.

In the third test case the strip looks like this:

It is easy to check that the unblocked squares on it can not be tiled.