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

int main(){
  string a,b; cin>>a>>b;

  static int need[26];
  for (char i: a) --need[i-'a'];
  for (char i: b) ++need[i-'a'];
  for (char i='a'; i<='z'; ++i) while (need[i-'a']-->0) a+=i;

  cout<<a<<endl;
}