#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
using ll = long long;
using ld = long double;
int main(void){
	string A,B;
	cin >> A >> B;
	int a = 0; int b = 0;;
	int c = 1;
	for(int i = A.size()-1; 0 <= i; --i){
		a += (A.at(i) - '0') * c;
		c *= 2;
	}
	c = 1;
	for(int i = B.size()-1; 0 <= i; --i){
		b += (B.at(i) - '0') * c;
		c *= 2;
	}
	cout << (a ^ b) << endl;
}