Ski Accidents

Description:

Input:

The first line contains a single positive integer $$$T$$$ — the number of test cases. $$$T$$$ test case description follows.

The first line of each description contains two integers $$$n$$$ and $$$m$$$ ($$$1 \leq n \leq 2 \cdot 10^5$$$) — the number of landing spots and tracks respectively.

The following $$$m$$$ lines describe the tracks. Each of these lines contains two integers $$$x$$$ and $$$y$$$ ($$$1 \leq x < y \leq n$$$) — indices of the starting and finishing spots for the respective track. It is guaranteed that at most two tracks start at each spot. There may be tracks in which starting and finishing spots both coincide.

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

Output:

For each test case, print a single integer $$$k$$$ ($$$0 \leq k \leq \frac{4}{7}n$$$) — the number of spots to be closed. In the next line, print $$$k$$$ distinct integers — indices of all spots to be closed, in any order.

If there are several answers, you may output any of them. Note that you don't have to minimize $$$k$$$. It can be shown that a suitable answer always exists.

Sample Input:

2
4 6
1 2
1 3
2 3
2 4
3 4
3 4
7 6
1 2
1 3
2 4
2 5
3 6
3 7

Sample Output:

2
3 4 
4
4 5 6 7 

Note:

In the first sample case, closing any two spots is suitable.

In the second sample case, closing only the spot $$$1$$$ is also suitable.