#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;

string to_binary(long bina){
    string ans = "";
    for(int i = 0; bina > 0; i++){
        ans = to_string(bina % 2) + ans;
        bina /= 2;
    }
    return ans;
}

long binary_to_num(string bina){
    long ans = 0;
    for(int i = 0; i < bina.size(); i++){
        ans += (bina[bina.size() - i - 1] - '0') * pow(2, i);
    }
    return ans;
}

int main(){
    long A, C;
    cin >> A >> C;
    string binaryA = to_binary(A), binaryC = to_binary(C), binaryB = "";
    for(int i = 0; i < binaryC.size() - binaryA.size(); i++){
        binaryA = "0" + binaryA;
    }
    for(int i = 0; i < binaryC.size(); i++){
        if(binaryA[i] == binaryC[i]){
            binaryB.push_back('0');        
        }else{
            binaryB.push_back('1');        
        }
    }
    cout << binary_to_num(binaryB) << endl;
}