#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef long double ld;
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <limits>
 
int main()
{
    string a, b; cin >> a >> b;
    string combine = a+b;
    sort(combine.begin(), combine.end());
    cout << combine << "\n";
    
    

    return 0;
}