#include<bits/stdc++.h>
#define int long long
using namespace std;
string s1,s2;
int f[1000];
string ans;
void dfs(int l1,int l2,int l3,int l4){
	if(l1>l2||l3>l4)return ;
	for(int i=l1;i<=l2;i++){
		if(s2[l3]==s1[i]){
			ans+=s1[i];
			string str=s2;
			string s;
			memset(f,0,sizeof(f));
			for(int j=l1;j<i;j++)f[s1[j]-'A']=1;
			for(int j=l3;j<=l4;j++)if(f[s2[j]-'A'])s+=s2[j];
			s2=s;
			dfs(0,i-1,0,s2.size()-1);
			s2=str;
			s="";
			memset(f,0,sizeof(f));
			for(int j=i+1;j<=l2;j++)f[s1[j]-'A']=1;
			for(int j=l3;j<=l4;j++)if(f[s2[j]-'A'])s+=s2[j];
			s2=s;
			dfs(i+1,l2,0,s2.size()-1);
			s2=str;
		}
	}
}
signed main(){
	cin>>s1>>s2;
	dfs(0,s1.size()-1,0,s2.size()-1);
	cout<<ans;
	return 0;
} 
//DBEAC
//ABCDE