这才是noip的水平（虽然也不是很难）

#include <iostream>
#include <string>
using namespace std;

void buildPreOrder(string in, string post) {
    if (in.empty()) return;
    
    char root = post.back();
    cout << root; // 先序遍历直接输出根节点
    
    int rootPos = in.find(root);
    string leftIn = in.substr(0, rootPos);
    string rightIn = in.substr(rootPos + 1);
    
    string leftPost = post.substr(0, leftIn.size());
    string rightPost = post.substr(leftIn.size(), rightIn.size());
    
    buildPreOrder(leftIn, leftPost);
    buildPreOrder(rightIn, rightPost);
}

int main() {
    string inOrder, postOrder;
    cin >> inOrder >> postOrder;
    buildPreOrder(inOrder, postOrder);
    cout << endl;
    return 0;
}