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

int main(){
	string A,B;
	cin>>A>>B;
	reverse(A.begin(),A.end());
	reverse(B.begin(),B.end());
	while(A.size()<B.size())A.push_back('0');
	while(B.size()<A.size())B.push_back('0');
	int ans=0;
	for(int i=0;i<A.size();i++){
		int t=(A[i]=='1')^(B[i]=='1');
		ans+=t<<i;
	}
	cout<<ans<<'\n';
}