#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>

using namespace std;


int main() {
	int i, j, k;   
	long long a, c;

	cin >> a >> c;

	bitset<50>aa(a);
	bitset<50>cc(c);

	//cout << aa << endl;

	string ast = aa.to_string();
	string cst = cc.to_string();
	string bst;

	for (i = 0; i < ast.length(); i++) {
		if (ast[i] == '1' && cst[i] == '0') {
			bst += '1';
		}
		else if (ast[i] == '0' && cst[i] == '0') {
			bst += '0';
		}
		else if (ast[i] == '1' && cst[i] == '1') {
			bst += '0';
		}
		else if (ast[i] == '0' && cst[i] == '1') {
			bst += '1';
		}
	}

	long long b = 0;
	long long keta = 1;

	for (i = bst.length() - 1; i >= 0; i--) {
		b += ((int)bst[i] - 48) * keta;

		keta *= 2;
	}

	cout << b << endl;


	getchar();
	getchar();
	return 0;
}