Selective Course

Time Limit: 2 Seconds
Memory Limit: 65536 KB

On the 18th week of each semester, teacher should schedule their exames. There
are at most 200 elective courses. And each student could select at most 2 courses
one semester. School always schedule 2 exam times a day, 8:30 - 10:30 in the morning
and 3:00-5:00 in the afternoon.

Your task is to calculate the mininum exam times.

**Input**

The input consists of several testcases.

In each test case, the first line contains n and m, n for the number of elective
course , m ( 0 < m <= 2000) for the number of student. Followed m line,
each line gives two integer coursei and coursej (coursei != coursej) which indicate
the courses selected by mth student.

Process to the end of file.

**Output**

For each testcase, exactly one line of output containing a single integer value
is to be produced.

**Sample Input**

4 5

1 2

2 3

3 4

1 4

2 4

**Sample Output**

3

Author:

**CHEN, Hong**
Source:

**ZOJ Monthly, January 2004**
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