#include <bits/stdc++.h>
using namespace std;

int main() {
    string a, b;
    while (cin >> a >> b) {
        const int S = 256;
        vector<int> c1(S), c2(S);
        for (char c : a) c1[c]++;
        for (char c : b) c2[c]++;
        string ans;
        for (int i = 0; i < S; i++) for (int j = 0; j < max(c1[i], c2[i]); j++) ans += (char)i;
        cout << ans << endl;
    }
}