National Property

题意翻译

给定一些字符串，其中字母用数字表示，并且初始是小写的。你可以把一些小写字母改成大写，但同时你要把所有同种字母全部改成大写。问是否能经过一些操作使得最终的字符串序列满足按字典序升序排列。如果能，则需要输出方案。

题目描述

You all know that the Library of Bookland is the largest library in the world. There are dozens of thousands of books in the library. Some long and uninteresting story was removed... The alphabet of Bookland is so large that its letters are denoted by positive integers. Each letter can be small or large, the large version of a letter $ x $ is denoted by $ x' $ . BSCII encoding, which is used everywhere in Bookland, is made in that way so that large letters are presented in the order of the numbers they are denoted by, and small letters are presented in the order of the numbers they are denoted by, but all large letters are before all small letters. For example, the following conditions hold: $ 2&lt;3 $ , $ 2'&lt;3' $ , $ 3'&lt;2 $ . A word $ x_{1},x_{2},...,x_{a} $ is not lexicographically greater than $ y_{1},y_{2},...,y_{b} $ if one of the two following conditions holds: - $ a<=b $ and $ x_{1}=y_{1},...,x_{a}=y_{a} $ , i.e. the first word is the prefix of the second word; - there is a position $ 1<=j<=min(a,b) $ , such that $ x_{1}=y_{1},...,x_{j-1}=y_{j-1} $ and $ x_{j}&lt;y_{j} $ , i.e. at the first position where the words differ the first word has a smaller letter than the second word has. For example, the word " $ 3' $ $ 7 $ $ 5 $ " is before the word " $ 2 $ $ 4' $ $ 6 $ " in lexicographical order. It is said that sequence of words is in lexicographical order if each word is not lexicographically greater than the next word in the sequence. Denis has a sequence of words consisting of small letters only. He wants to change some letters to large (let's call this process a capitalization) in such a way that the sequence of words is in lexicographical order. However, he soon realized that for some reason he can't change a single letter in a single word. He only can choose a letter and change all of its occurrences in all words to large letters. He can perform this operation any number of times with arbitrary letters of Bookland's alphabet. Help Denis to choose which letters he needs to capitalize (make large) in order to make the sequence of words lexicographically ordered, or determine that it is impossible. Note that some words can be equal.

输入输出格式

输入格式

The first line contains two integers $ n $ and $ m $ ( $ 2<=n<=100000 $ , $ 1<=m<=100000 $ ) — the number of words and the number of letters in Bookland's alphabet, respectively. The letters of Bookland's alphabet are denoted by integers from $ 1 $ to $ m $ . Each of the next $ n $ lines contains a description of one word in format $ l_{i},s_{i,1},s_{i,2},...,s_{i,li} $ ( $ 1<=l_{i}<=100000 $ , $ 1<=s_{i,j}<=m $ ), where $ l_{i} $ is the length of the word, and $ s_{i,j} $ is the sequence of letters in the word. The words are given in the order Denis has them in the sequence. It is guaranteed that the total length of all words is not greater than $ 100000 $ .

输出格式

In the first line print "Yes" (without quotes), if it is possible to capitalize some set of letters in such a way that the sequence of words becomes lexicographically ordered. Otherwise, print "No" (without quotes). If the required is possible, in the second line print $ k $ — the number of letters Denis has to capitalize (make large), and in the third line print $ k $ distinct integers — these letters. Note that you don't need to minimize the value $ k $ . You can print the letters in any order. If there are multiple answers, print any of them.

输入输出样例

输入样例 #1

4 3
1 2
1 1
3 1 3 2
2 1 1

输出样例 #1

Yes
2
2 3 

输入样例 #2

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

输出样例 #2

Yes
0

输入样例 #3

4 3
4 3 2 2 1
3 1 1 3
3 2 3 3
2 3 1

输出样例 #3

No

说明

In the first example after Denis makes letters $ 2 $ and $ 3 $ large, the sequence looks like the following: - $ 2' $ - $ 1 $ - $ 1 $ $ 3' $ $ 2' $ - $ 1 $ $ 1 $ The condition $ 2'&lt;1 $ holds, so the first word is not lexicographically larger than the second word. The second word is the prefix of the third word, so the are in lexicographical order. As the first letters of the third and the fourth words are the same, and $ 3'&lt;1 $ , then the third word is not lexicographically larger than the fourth word. In the second example the words are in lexicographical order from the beginning, so Denis can do nothing. In the third example there is no set of letters such that if Denis capitalizes them, the sequence becomes lexicographically ordered.