序列Z=<B，C，D，B>是序列X=<A，B，C，B，D，A，B>的子序列，相应的递增下标序列为<2，3，5，7>。



一般地，给定一个序列X=<x1,x2,…,xm>，则另一个序列Z=<z1,z2,…,zk>是X的子序列，是指存在一个严格递增的下标序列〈i1,i2,…,ik〉使得对于所有j=1,2,…,k使Z中第j个元素zj与X中第ij个元素相同。



给定2个序列X和Y，当另一序列Z既是X的子序列又是Y的子序列时，称Z是序列X和Y的公共子序列。



你的任务是：给定2个序列X、Y，求X和Y的最长公共子序列Z。

-Sequence Z = <B，C，D，B> Is a sequence X = <A，B，C，B，D，A，B> Sub-sequence, the corresponding sequence of increasing subscr ipt < 2,3,5,7> . In general, given a sequence X = <x1,x2,…,xm> , Another sequence Z = <z1,z2,…,zk> Subsequence of X, there is a strictly increasing sequence < i1,i2,…,ik>　subscr ipt such that for all j = 1,2, ..., k so that the first j elements Z and X in the ij zj the same elements. Given two sequences X and Y, when another sequence Z is X, Y sequence is the sequence when said sequence of X and Y, Z is the common sub-sequences. Your task is: given two sequences X, Y, X and Y find the longest common subsequence Z.