#include <iostream>
#include <fstream>
#include <string.h>

using namespace std;

fstream f("date.in");
char primul[200], doilea[200];
int  s[200], maxim[200], n, marime, sol;

void     delimitare()
{
    char i1[200], i2[200];
    int n1[10], n2[10], i, j;
    f.getline(i1, 200, '\n');
    f.getline(i2, 200, '\0');

    i = 0;

    for (i = 0; i <= 9; i++)
    {
        n1[i] = 0;
        n2[i] = 0;
    }

    i = 0;
    while (i1[i] != '\0')
    {
        n1[i1[i] - '0'] = 1;
        i++;
    }

    i = 0;
    while (i2[i] != '\0')
    {
        n2[i2[i] - '0'] = 1;
        i++;
    }

    i = 0;
    j = 0;
    while (i1[i] != '\0')
    {
        if (n2[i1[i] - '0'] == 1 && n1[i1[i] - '0'] == 1)
        {
            primul[j] = i1[i];
            j++;
        }
        i++;
    }
    primul[j] = '\0';

    i = 0;
    j = 0;
     while (i2[i] != '\0')
    {
        if (n2[i2[i] - '0'] == 1 && n1[i2[i] - '0'] == 1)
        {
            doilea[j] = i2[i];
            j++;
        }
        i++;
    }
    doilea[j] = '\0';
}

void     init(int k)
{
    if (k == 0)
        s[k] = -1;
    else
        s[k] = s[k - 1];
}

int     next(int k)
{
    if (s[k] < int(strlen(primul) - 1))
    {
        s[k]++;
        return (1);
    }
    else
        return (0);
}

int     valid(int k)
{
    int i, j;
    i = 0;
    j = 0;
    while (i <= k && doilea[j] != '\0')
    {
        while (doilea[j] != primul[s[i]] && doilea[j] != '\0')
            j++;
        i++;
    }
    if (i != (k + 1))
        return (0);
    else
        return (1);

}

int     solutie(int k)
{
    return k == (marime - 1);
}

void     afisare(int k)
{
    for (int i = 0; i <= k; i++)
        cout << primul[maxim[i]];
    cout << endl;
}

int    comparatie(int maxim[200], int s[200], int k)
{
    int i;

    i = 0;
    while (maxim[i] == s[i] && k < strlen(primul))
        i++;
    if (primul[s[i]] > primul[maxim[i]])
        return (1);
    return (0);
}

void    depunere(int k)
{
    if (sol == 0)
        for (int i = 0; i <= k; i++)
            maxim[i] = s[i];
    else
        if (comparatie(maxim, s, k))
            for (int i = 0; i <= k; i++)
                maxim[i] = s[i];
    sol = 1;
}

void    bt()
{
    int k = 0;

    init(k);
    while (k >= 0)
    {
        if (next(k))
        {
            if (valid(k))
            {
                if (solutie(k))
                    depunere(k);
                else
                {
                    k++;
                    init(k);
                }
            }
        }
        else k--;
    }
}

void    interschimb()
{
    int marime_1 = strlen(primul);
    int marime_2 = strlen(doilea);
    char inter[200];
    for (int i = 0; i <= marime_1; i++)
        inter[i] = primul[i];
    for (int i = 0; i <= marime_2; i++)
        primul[i] = doilea[i];
    for (int i = 0; i <= marime_1; i++)
        doilea[i] = inter[i];
}

int main()
{
    delimitare();
    sol = 0;

    if (strlen(primul) > strlen(doilea))
        interschimb();

    if (strlen(primul) == 0 || strlen(doilea) == 0)
        cout << "0";
    else
        for (int i = strlen(primul); i > 0 && sol == 0; i--)
        {
            marime = i;
            bt();
        }
    afisare(marime - 1);
    return 0;
}