#include<iostream>
#include <bits/stdc++.h>

#define ll long long
#define IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
const int N = 1e6 + 5, mod = 998244353;


void doWork() {
    string a, b;
    cin >> a >> b;
    string ans = a + b;
    sort(ans.begin(), ans.end());
    cout << ans;
}

int main() {
    IO
    int t = 1;
    //cin >> t;
    for (int i = 1; i <= t; i++) {
        //  cout << "Case #" << i << ": ";
        doWork();
    }
}