#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
using namespace std;
struct Tree 
{
    char num;
    Tree *left=NULL,*right=NULL;
};
char a[100],b[100];
int len;
void dfs(Tree *k)
{
    if(k==NULL) return;
    dfs(k->left);
    cout<<k->num;
    dfs(k->right);
}
Tree *build(char *x,char *y,int l)
{
    Tree *node = NULL;
    for(int i=0;i<l;i++)
    {
        // cerr<<"Running"<<endl;
        if(x[0]==y[i])
        {
            node = new Tree();
            node->num=x[0];
            node->left = build(x+1,y,i);
            node->right = build(x+i+1,y+i+1,l-i+1);
        }
    }
    return node;
}
int main()
{
    string s1,s2;
    getline(cin,s1);
    getline(cin,s2);
    len=s1.size();
    for(int i=0;i<len;i++)
    {
        a[i]=s1[i];
        b[i]=s2[i];
    }
    Tree *root = build(a,b,len);
    dfs(root);
    return 0;
}