import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Tester2 {
	public static void main(String[] args){
		try(BufferedReader br = new BufferedReader(new InputStreamReader(System.in))){
			String[] ary = br.readLine().split(" ");
			long a = Long.parseLong(ary[0]);
			long b = Long.parseLong(ary[1]);
			System.out.println(a^b);
		}catch(IOException e) {
			e.printStackTrace();
		}
	}
}