文件目录

#include <bits/stdc++.h>
using namespace std;
void getxx(string zx, string cx)
{
    if (cx.size() == 0)
        return;
    char root = cx[0];
    int id = zx.find(root);
    string zxl = zx.substr(0, id), zxr = zx.substr(id + 1), cxl = "", cxr = "";
    for (int i = 1; i < cx.size(); i++)
        if (zxl.find(cx[i]) == string::npos)
            cxr += cx[i];
        else
            cxl += cx[i];
    cout << root;
    getxx(zxl, cxl);
    getxx(zxr, cxr);
}
int main()
{
    string zx, cx;
    cin >> zx >> cx;
    getxx(zx, cx);
    return 0;
}