#include <bits/stdc++.h>
using namespace std;
#define AC cin.sync_with_stdio(0),cin.tie(0);
int preord[1000000],inord[1000000];
void tree( int pre ,int in, int root){
int leftN;
//leftN = left tree nodes and leaves total cnt
for(int i=0;i<root;i++){
if(inord[i+in] == preord[pre]) leftN = i;
}
//cout<<root<<" "<<leftN<<"\n";
//left
if(leftN != 0 ){
tree(pre+1,in, leftN );
}
if(leftN != root-1){
//right not empty
tree(pre+1+leftN, in+1+leftN, root-leftN-1);
}
cout<<char('A'-1+preord[pre]);//leaf and node
}
int main(){
AC
string tmp1,tmp2;
cin>>tmp1>>tmp2;
for(int i=0;i<tmp1.length();i++){
preord[i]=tmp1[i]-'A'+1;
inord[i] =tmp2[i]-'A'+1;
//cout<<preord[i]<<" ";
}
//cout<<"\n";
//preoder: mid->left->right
//inorder: left->mid->right
//postorder: left->right->mid
tree(0,0,tmp1.length());
cout<<"\n";
return 0;
}
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