Projectors

The cows are attending Cow School, which is famous for its multi-media
presentations; every class at Cow School uses a projector.

Cow School is also famous for being cheap. Cow School is so thrifty
that the administration will purchase only the minimum number of
projectors needed for its N (1 <= N <= 200) classes, conveniently
numbered 1..N.

Cow School is also too frugal to hire staff to carry the projectors
between classes. Since each class is in a different classroom, this
becomes a fairly large task. Thus, Cow School has its M (1 <= M <=
2,000) bovine students carry projectors between classes. Each cow
attends exactly two classes during the day, and can carry arbitrarily
many projectors from her first class to her second class. (Each
class needs only one projector, but a cow might need to bring several
projectors to a class so that other cows there can afterwards take
the projectors to several later classes.)

The administration has compiled a list of the classes attended by
all the cows. Each cow i has a first class A_i and a second class
B_i (1 <= A_i < B_i <= N). The administration will buy the minimum
number of projectors needed and put them in any given classroom as
needed at the start of the day.

Write a program to determine the minimum number of projectors that
need to be purchased so that every class can have a projector.

PROBLEM NAME: project

INPUT FORMAT:

* Line 1: Two integers: N and M

* Lines 2..M+1: Line i+1 lists two class numbers: A_i and B_i

SAMPLE INPUT:

4 4
1 2
2 3
2 4
1 4

INPUT DETAILS:

There are 4 classes; it's possible to carry projectors from class
1 to classes 2 and 4 and from class 2 to classes 3 and 4.

OUTPUT FORMAT:

* Line 1: The minimum number of projectors the administration needs to
        buy.

SAMPLE OUTPUT:

2

OUTPUT DETAILS:

Projectors are carried along the following paths:
1->2->3
1->4