#include<bits/stdc++.h>
using namespace std;
string a,b;
void work(string a,string b){
	if(a.empty())return;
	char root(a[0]);int k(b.find(root));
	a.erase(a.begin());
	string lefta(a.substr(0,k)),righta(a.substr(k)),leftb(b.substr(0,k)),rightb(b.substr(k+1));
	work(lefta,leftb),work(righta,rightb);
	putchar(root);
}
int main(){
	getline(cin,b);
	getline(cin,a);
	work(a,b);
	putchar('\n');
	return 0;
}

输入: F F 输出: F