#include <stdio.h>
#include <math.h>

int main() {
    int a,b,i=0,count=0;
    scanf("%d %d",&a, &b);

    /* 桁数を計算 */
    while (a >> abs(i) != 0) {
        if ((a >> abs(i)) & 0x01 && (b >> abs(i)) & 0x01){
            count -= (int)pow(2, abs(i)) ;
        }
        i--;
    }
    printf("%d\n", (a|b)-count);
    return 0;
}