Feeding the cows   feeding.X

Many people don't know that cows are so hungry they can barely make
it through each night. Each morning, Farmer John rushes to feed his
N cows (1 <= N <= 20,000) their breakfast of hay which he distributes
in T (1 <= T <= 20,000) feedbags conveniently numbered 1..T, each
of which is strapped onto a single cow. Ever picky, each cow has
two favorite feedbags, and will only eat from one of those two and
not from any other. The constraints on the number and desirability
mean that Farmer John might not be able to feed all the cows at the
same time.

Farmer John can choose which cows to feed and which feedbags to use
for that feeding for each cow. Determine the maximum number of cows
he can feed at the same time.

PROBLEM NAME: feeding

INPUT FORMAT:

* Line 1: Two space-separated integers, N and T

* Lines 2..N+1: Each line contains two distinct space-separated
        integers, which are the favorite feedbags of one cow.

SAMPLE INPUT:

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

OUTPUT FORMAT:

* Line 1: The maximum number of cows that can feed at the same time.

SAMPLE OUTPUT:

5

OUTPUT DETAILS:

If the cow with favorites (4, 6) is omitted, the others can all be fed 
simultaneously.