2926. Girls and Boys

单点时限: 5.0 sec

内存限制: 256 MB

In the second year of the university somebody started a study on the romantic relations between the students. The relation “romantically involved” is defined between one girl and one boy. For the study reasons it is necessary to find out the maximum set satisfying the condition: there are no two students in the set who have been “romantically involved”. The result of the program is the number of students in such a set.

输入格式

The input contains several data sets in text format. Each data set represents one set of subjects of the study, with the following description:

the number of students

the description of each student, in the following format

student_identifier:(number_of_romantic_relations) student_identifier1 student_identifier2 student_identifier3 ... 

or

student_identifier:(0)

The student_identifier is an integer number between $0$ and $n-1$ $(n \le 500)$, for $n$ subjects.

输出格式

For each given data set, the program should write to standard output a line containing the result.

样例

Input
7
0: (3) 4 5 6
1: (2) 4 6
2: (0)
3: (0)
4: (2) 0 1
5: (1) 0
6: (2) 0 1
3
0: (2) 1 2
1: (1) 0
2: (1) 0
Output
5
2

1 人解决,51 人已尝试。

3 份提交通过,共有 116 份提交。

9.9 EMB 奖励。

创建: 9 年前.

修改: 2 年,10 月前.

最后提交: 4 月,1 周前.

来源: Southeastern Europe 2000

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