遞歸
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<stack>
#include<cmath>
#include<vector>
#include<map>
using namespace std;
string s1,s2;
void dfs(string be,string en)
{
if(be.size())
{
char ch=en.at(en.size()-1);
cout<<ch;//輸出根
int k=be.find(ch);
dfs(be.substr(0,k),en.substr(0,k));
dfs(be.substr(k+1),en.substr(k,be.size()-k-1));
}
}
int main()
{
cin>>s1>>s2;
dfs(s1,s2);
return 0;
}