Girls and Boys

Time Limit: 10 Seconds
Memory Limit: 32768 KB

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.

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, for n subjects.

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

An example is given in Figure 1.

**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

Source:

**Southeastern Europe 2000**
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