import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Solution to Field Trip
 * 
 * @author vanb
 */
public class fieldtrip_vanb
{
    /** Input. */
    private static Scanner sc;
    
    /** Output. */
    private static PrintStream ps;
    
    /**
     * Do it!
     */
    private void doit()
    {
        int counts[] = new int[26];
        Arrays.fill( counts, 0 );
        for( int i=0; i<2; i++ )
        {
            char letters[] = sc.next().toCharArray();
            for( char letter : letters ) ++counts[letter-'a'];
        }
        
        for( int i=0; i<26; i++ )
        {
            for( int j=0; j<counts[i]; j++ ) ps.print( (char)('a'+i) );
        }
        ps.println();
    }
        
    /**
     * Main.
     * 
     * @param args unused
     * @throws Exception
     */
    public static void main( String[] args ) throws Exception
    {
        sc = new Scanner( System.in );
        ps = System.out;
        
        new fieldtrip_vanb().doit();
    }

}