#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("cifre.in");
ofstream fout ("cifre.out");
int main ()
{
    int a , b , v[10] = {0}, c ;
    cin >> a >> b  ;
    while (a)
    {
        c=a%10;
        v[c]++;
        a/=10;
    }
    while (b)
    {
        c=b%10;
        v[c]++;
        b/=10;
    }
    for(c=9; c >=0 ; c--)
        while (v[c])
        {
            cout << c ;
            v[c]--;
        }

return 0 ;
}