#include <bits/stdc++.h>
using namespace std;

struct tnode{
    char val;
    struct tnode* left,* right;
    tnode(char val):val(val),left(nullptr),right(nullptr){}
};

tnode* buildTree(string inOrder,string postOrder){
    if(postOrder.empty())return nullptr;
    char rootval=postOrder[postOrder.size()-1];
    int inPos=inOrder.find(rootval);
    tnode* root=new tnode(rootval);
    root->left=buildTree(inOrder.substr(0,inPos),postOrder.substr(0,inPos));
    root->right=buildTree(inOrder.substr(inPos+1),postOrder.substr(inPos,postOrder.size()-1-inPos));
    root->val=rootval;
    return root;
}

void preOrder(tnode *root){
    if(root==nullptr)return;
    cout<<root->val;
    preOrder(root->left);
    preOrder(root->right);
}

int main(){
    string in,post;
    while(cin>>in>>post){
        preOrder(buildTree(in,post));
    }
}

思路基本上和先序中序创建是一样的，主要是这里会使用后续字符串，就使用后续输出，中序依然是辅助字符串，确认左右子树的长度用