Longest Common Subsequence Again

Everyone knows LCS problem:

For example:
str1 = "GCTAT"
str2 = "CGATTA"

the longest common subsequence is "GTT" of them.So you should print "3".

I'm sure you can easily sovle it.So the challenge is coming again.(^_^)

For each case,there are two lines.one is string A,the other is string B.
the string Process to end of file.Each string will have at most 30000 characters.
All the characters are in upper-case.

For each case, output the maximum-length common subsequence.

GCTAT
CGATTA 

ABCFBC
ABFCAB

3
4

HDOJ 2008 Summer Exercise（4）- Buffet Dinner