#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <math.h>
using namespace std;


int main(void)
{
    unsigned long long a, c;
    unsigned long long b = 0;
    cin >> a >> c;

    for(int i = 0; a!=0||c!=0; i++)
    {
        b += pow(2,i)*(a%2!=c%2);
        a /= 2;
        c /= 2;
    }
    cout << b;
    return 0;
}