import java.util.Arrays;
import java.util.Scanner;

public class Main {
	
	public static long MOD = 1000000007;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final long A = sc.nextLong();
		final long C = sc.nextLong();
		
		System.out.println(A ^ C);
	}
}