#include <cstdio>

int m, n;

int main()

{

 scanf("%d%d", &m, &n);

 int u = m & n;

 int v = m ^ n;

 while (u) {

 int s = v;

 int t = u << 1;

 u = s & t;

 v = s ^ t;

 }

 printf("%d\n", v);

}