#include <bits/stdc++.h>
using namespace std;

int main() {
	string a, b;
	cin >> a >> b;

	long long an = 0, bn = 0;
	for( int i = 0; i < (int)a.size(); i++ ) an = an * 2 + a[i] - '0';
	for( int i = 0; i < (int)b.size(); i++ ) bn = bn * 2 + b[i] - '0';
	cout << (an ^ bn) << endl;
}