import java.util.Scanner;

public class ClassFieldTrip {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

String ann = sc.nextLine();

String ben = sc.nextLine();

char[] both = (ann+ben).toCharArray();

mergeSort(both);

System.out.println(both);

}

public static void mergeSort(char[] arr) {

//base case

if(arr.length == 1) return;

//recursive call

int leftLength = arr.length/2;

int rightLength = arr.length-arr.length/2;

char[] left = new char[leftLength];

for (int i = 0; i < left.length; i++) {

left[i] = arr[i];

}

char[] right = new char[rightLength];

for (int i = 0; i < right.length; i++) {

right[i] = arr[leftLength+i];

}

mergeSort(left);

mergeSort(right);

merge(left,right,arr);

}

public static void merge(char[] left, char[] right, char[] original) {

int i = 0, j = 0, k = 0;

while(i<left.length && j<right.length){

if(left[i] < right[j]){

original[k] = left[i];

i++;

}

else{

original[k] = right[j];

j++;

}

k++;

}

while(i<left.length){

original[k] = left[i];

i++;

k++;

}

while(j<right.length){

original[k] = right[j];

j++;

k++;

}

}

}