/// Author : shohanur Rahaman
/// URI 1026 (To Carry or not to Carry)

#include<stdio.h>

// bitwise XOR ^
//              AND &
//              NAND ~
//              OR     |

int main()
{

   int unsigned long  a,b,c;

   while(scanf("%lu %lu",&a,&b)==2){
            c=(a^b);

    printf("%lu\n",c);
}
    return 0;
}