#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
using bigint = boost::multiprecision::cpp_int;

template <typename T> using min_priority_queue = priority_queue<T,vector<T>,greater<T>>;

random_device seed_gen;
mt19937 engine(seed_gen());

bigint x(bigint a, bigint b) {
    if(a == 0) return b;
    if(b == 0) return a;
    if(a == b) return 0;

    return x(a / 2, b / 2) * 2 + x(a % 2, b % 2);
}

int main() {
    bigint a, b;
    cin >> a >> b;
    cout << x(a, b) << endl;
}