bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;
import java.io.IOException;

public class JavaApplication13  {      
static Character[] ans;
static String O;
static String I;
static Character[] Ochar;
static Character[] Ichar;
static int n;


    public static void main(String[] args) throws IOException{
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    PrintWriter pw = new PrintWriter(System.out);
    //StringTokenizer st = new StringTokenizer(br.readLine());
    O = br.readLine();
    I = br.readLine();
    n = O.length();
    Ochar = new Character[n];
    Ichar = new Character[n];
    ans = new Character[n];
    
    for(int i = 0;i<n;i++)
    {
        Ochar[i]=O.charAt(i);
        Ichar[i]=I.charAt(i);
    }
    Arrays.sort(Ochar);
    Arrays.sort(Ichar);
    boolean weird = (Ichar[n-1]<Ochar[0]);
    int front = 0;
    int back = n-1;
    int Ofront = 0;
    //int Oback = -1;
    //int Ifront = 0;
    int Iback = n-1;    
    for(int i =0;i<n;i++)
    {
       if(!weird)
       {if(i%2==0)
       {ans[front]=Ochar[Ofront];
        front++;
        Ofront++;
        
       }
       else{
       ans[front]=Ichar[Iback];
       front++;
       Iback--;
       }
       weird = (Ichar[Iback]<Ochar[Ofront]);
       }
       else{
       if(i%2==0)
       {
           ans[back]=Ochar[Ofront];
           back--;
           Ofront++;
       }
       else{
       ans[back]=Ichar[Iback];
       back--;
       Iback--;
       }
       }
       
    }
    
    for(int i =0;i<n;i++)
    {
        pw.print(ans[i]);
    }
    pw.close();
    }
       
}