#include <iostream>
using namespace std;

int p(int x, int y) {
    if(x == 0) return y;
    if(y == 0) return x;

    int s = x ^ y;
    int t = (x & y) << 1;
    return p(s, t);
}

int main(){
    int a, b;
    cin >> a >> b;
    cout << p(a, b) << endl;
    return 0;
}