/* -*- coding: utf-8 -*-
 *
 * 3149.cc:  No.3149 find X which satisfies with equlation - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* main */

int main() {
  int a, b;
  scanf("%d%d", &a, &b);

  printf("%d\n", a ^ b);

  return 0;
}