Problem F
                                          Herding Cats
                                     Time limit: 2 seconds
You are opening a cat cafe in Baku and would like to take a promotional photograph of all the cats sitting
in the front window. Unfortunately, getting cats to do what you want is a famously hard problem. But
you have a plan: you have bought a collection of m catnip plants, each of a different variety, knowing
that each cat likes some of these varieties. There is a row of m pots in the window, numbered 1 to m in
order, and you will place one plant in each pot. Each cat will then be persuaded (by means of a toy on a
string) to walk along the row of pots from 1 to m. As soon as a cat reaches a pot with a catnip plant that
it likes, it will stop there, even if there already are other cats at that plant.

                  Figure F.1: One possible plant ordering for the first sample test case.

You know which pot you would like each cat to stop beside. Can you find a way in which to place the
plants in the pots to achieve this?

Input

The first line of input contains an integer t (1 ≤ t ≤ 10 000), which is the number of test cases. The
descriptions of t test cases follow.
The first line of each test case contains two integers n and m, where n (1 ≤ n ≤ 2 · 105 ) is the number
of cats, and m (1 ≤ m ≤ 2 · 105 ) is the number of catnip plants (and also the number of pots). Catnip
plants are numbered from 1 to m.
The following n lines each describe one cat. The line starts with two integers p and k, where p (1 ≤
p ≤ m) is the pot at which the cat should stop, and k (1 ≤ k ≤ m) is the number of catnip plants the cat
likes. The remainder of the line contains k distinct integers, which are the numbers of the plants that the
cat likes.
Over all test cases, the sum of n is at most 2 · 105 , the sum of m is at most 2 · 105 , and the sum of all k
is at most 5 · 105 .

49th ICPC World Championship Problem F: Herding Cats © ICPC Foundation                                    11

Output

For each test case, output either yes if it is possible to arrange the catnip plants as described above, or
no if not.

 Sample Input 1                                           Sample Output 1
 2                                                        yes
 3   5                                                    no
 2   2   1 5
 2   3   1 4 5
 4   2   3 4
 3   5
 2   2   1 5
 2   3   1 4 5
 5   2   3 4

Explanation of Sample 1: In the first test case, a possible ordering of the plants is [2, 1, 5, 3, 4]. This
way, cat 1 will stop at pot 2, as it is the first pot with a plant variety that it likes. Cat 2 will stop there as
well. Cat 3 will continue all the way to pot 4, as shown in Figure F.1.

49th ICPC World Championship Problem F: Herding Cats © ICPC Foundation                                         12