#include<bits/stdc++.h>
using namespace std;
int main(){
	string S,T;
	cin>>S>>T;
	int A=stoi(S,nullptr,2);
	int B=stoi(T,nullptr,2);
	assert(0<=A&&A<(1<<30));
	assert(0<=B&&B<(1<<30));
	int ans=A^B;
	cout<<ans<<endl;
}