题解在此

#include <iostream>
#include <string>
using namespace std;
void dfs(string s1,string s2){
    if (s1.size()==0){
        return;
    }
    int id=s1.find(s2.back());
    cout<<s1[id];
    dfs(s1.substr(0,id),s2.substr(0,id));
    dfs(s1.substr(id****1.size()-id-1),s2.substr(id,s1.size()-id-1));
}
int main(){
    string s1,s2;
    cin>>s1>>s2;
    dfs(s1,s2);
    return 0;
}