Cheops and a Contest (Easy Version)
Contest: Codeforces Round 990 (Div. 1)
Difficulty rating: 2900
Tags: constructive algorithms, greedy

This is the easy version of the problem. The difference between the versions is that in this version, $$$m$$$ equals $$$2$$$. You can hack only if you solved all versions of this problem.

There is a problem-solving competition in Ancient Egypt with $$$n$$$ participants, numbered from $$$1$$$ to $$$n$$$. Each participant comes from a certain city; the cities are numbered from $$$1$$$ to $$$m$$$. There is at least one participant from each city.

The $$$i$$$-th participant has strength $$$a_i$$$, specialization $$$s_i$$$, and wisdom $$$b_i$$$, so that $$$b_i \ge a_i$$$. Each problem in the competition will have a difficulty $$$d$$$ and a unique topic $$$t$$$. The $$$i$$$-th participant will solve the problem if

- $$$a_i \ge d$$$, i.e., their strength is not less than the problem's difficulty, or
- $$$s_i = t$$$, and $$$b_i \ge d$$$, i.e., their specialization matches the problem's topic, and their wisdom is not less than the problem's difficulty.

Cheops wants to choose the problems in such a way that each participant from city $$$i$$$ will solve strictly more problems than each participant from city $$$j$$$, for all $$$i < j$$$.

Please find a set of at most $$$5n$$$ problems, where the topics of all problems are distinct, so that Cheops' will is satisfied, or state that it is impossible.

Input format:
Each test contains multiple test cases. The first line contains the number of test cases $$$T$$$ ($$$1 \le T \le 10^4$$$). The description of the test cases follows.

The first line of each test case contains two integers $$$n$$$, $$$m$$$ ($$$2 \mathbf{=} m \le n \le 3 \cdot {10}^5$$$) — the number of participants and the number of cities.

The following $$$n$$$ lines describe the participants. The $$$i$$$-th line contains three integers —$$$a_i$$$, $$$b_i$$$, $$$s_i$$$ ($$$0 \le a_i, b_i, s_i \le {10}^9$$$, $$$a_i \le b_i$$$) — strength, wisdom, and specialization of the $$$i$$$-th participant, respectively.

The next $$$m$$$ lines describe the cities. In the $$$i$$$-th line, the first number is an integer $$$k_i$$$ ($$$1 \le k_i \le n$$$) — the number of participants from the $$$i$$$-th city. It is followed by $$$k_i$$$ integers $$$q_{i, 1}, q_{i, 2}, \ldots, q_{i, k_i}$$$ — ($$$1 \le q_{i, j} \le n$$$, $$$1 \le j \le k_i$$$) — the indices of the participants from this city. It is guaranteed that each participant is mentioned exactly once.

It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$3 \cdot 10^5$$$.

Output format:
For each test case, if there exists a set of problems that satisfies Cheops' conditions, then in the first line output a single integer $$$p$$$ ($$$1 \le p \le 5n$$$) — the number of problems in your solution.

Then output $$$p$$$ lines, each containing two integers $$$d$$$ and $$$t$$$ ($$$0 \le d, t \le {10}^9$$$) — the difficulty and topic of the respective problem. The topics must be distinct.

If there is no set of problems that meets Cheops' wishes, print $$$-1$$$ instead.

Constraints:
Time limit: 4.0 s
Memory limit: 512.0 MB

Example input:
2
5 2
5 7 1
6 7 2
3 9 2
5 10 3
4 4 1
2 1 2
3 3 4 5
2 2
1 2 1
1 2 1
1 2
1 1

Example output:
7
6 4
6 5
5 6
5 7
4 8
4 9
7 1
-1

Editorial: