#4CombineListsOfLetters

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

public class CombineListsOfLetters {

    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        List<String> firstList = new ArrayList<String>();
        firstList.add(scan.nextLine());
        List<String> secondList = new ArrayList<String>();
        secondList.add(scan.nextLine());
        List<String> newList = new ArrayList<>();
        newList.addAll(firstList);
        newList.addAll(secondList);
        HashSet<String> hs = new HashSet<>(firstList);
        firstList.removeAll(newList);
        newList.removeAll(hs);
        System.out.print(newList);
    }

}