CF615A.Bulbs

Vasya wants to turn on Christmas lights consisting of m bulbs. Initially, all bulbs are turned off. There are n buttons, each of them is connected to some set of bulbs. Vasya can press any of these buttons. When the button is pressed, it turns on all the bulbs it's connected to. Can Vasya light up all the bulbs?

If Vasya presses the button such that some bulbs connected to it are already turned on, they do not change their state, i.e. remain turned on.

瓦西娅想要打开由 $m$ 个灯泡组成的圣诞彩灯。初始时，所有灯泡均处于关闭状态。共有 $n$ 个按钮，每个按钮连接到某一些灯泡。瓦西娅可以按下其中任意一个按钮。当按下某个按钮时，它会打开所有与之相连的灯泡。瓦西娅能否点亮所有灯泡？

如果瓦西娅按下的按钮所连接的某些灯泡已经处于开启状态，则这些灯泡的状态不会改变，即仍保持开启。

The first line of the input contains integers n and m (1 ≤ n, m ≤ 100) — the number of buttons and the number of bulbs respectively.

Each of the next n lines contains x__i (0 ≤ x__i ≤ m) — the number of bulbs that are turned on by the i-th button, and then x__i numbers y__ij (1 ≤ y__ij ≤ m) — the numbers of these bulbs.

输入的第一行包含两个整数 $n$ 和 $m$（$1 \le n, m \le 100$），分别表示按钮的数量和灯泡的数量。

接下来的 $n$ 行中，每行首先给出一个整数 $x_i$（$0 \le x_i \le m$）—— 表示第 $i$ 个按钮所控制的开启灯泡的数量，随后是 $x_i$ 个整数 $y_{ij}$（$1 \le y_{ij} \le m$）—— 表示这些灯泡的编号。

If it's possible to turn on all m bulbs print "YES", otherwise print "NO".

如果可以打开所有 $m$ 个灯泡，则输出 "YES"，否则输出 "NO"。

In the first sample you can press each button once and turn on all the bulbs. In the 2 sample it is impossible to turn on the 3-rd lamp.

在第一个样例中，你可以对每个按钮各按一次，从而打开所有灯泡。在第二个样例中，无法打开第三个灯泡。