#include<bits/stdc++.h>

using namespace std;

int main(){
    string x , y; cin >> x >> y;
    int i = 0 , j = 0;
    string ans ;
    sort(x.begin(), x.end());
    sort(y.begin(), y.end());
    while (i < x.size() && j < y.size()){
        if(x[i] < y[j]){
            ans += x[i];
            i++;
        }else{
            ans += y[j++];
        }
    }
    while(i < x.size()) ans+=x[i++];
    while(j < y.size()) ans+=y[j++];
    cout << ans << endl;
}