#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	string A, B;
	cin >> A >> B;

	string C;

	int base = 1;
	int ans = 0;

	if (A.length() < B.length()) {
		C = A;
		A = B;
		B = C;
	}

	for (unsigned int i = 1; i <= B.length(); i++) {
		if (A[A.length() - i] == B[B.length() - i]) {
			A[A.length() - i] = '0';
		}
		else {
			A[A.length() - i] = '1';
		}
	}

	for (unsigned int i = A.length(); i > 0; i--) {
		if (A[i - 1] == '1') {
			ans += base;
		}
		base *= 2;
	}

	cout << ans << endl;

	return 0;

}