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

void dfs(string mid, string post)
{
    if(mid=="") return;
    int n=post.length();
    char c=post[n-1];
    cout<<c;
    string m="", p="";
    int i;
    for(i=0; mid[i]!=c; i++)
    {
        m+=mid[i];
        p+=post[i];
    }
    dfs(m, p);
    i++;
    m="", p="";
    for(; i<n; i++)
    {
        m+=mid[i];
        p+=post[i];
    }
    dfs(m, p);
}

int main()
{
    string mid, post;
    cin>>mid>>post;
    dfs(mid, post);
    return 0;
}

(标题应该说的够清楚了吧，蒟蒻求助