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

void solve();

signed main(){
	cin.tie(nullptr)->sync_with_stdio(false);
	cout<<fixed<<setprecision(15);

	int T=1;

	//cin>>T;
	
	while(T--)solve();

	return 0;
}

void solve(){
	string A,B;
	cin>>A>>B;
	if(A.size()>B.size())swap(A,B);
	while(A.size()<B.size())A="0"+A;
	int ans=0;
	for(int i=A.size()-1,a=0;i>=0;--i,++a){
		if(A[i]=='1'&&B[i]=='1')continue;
		else if(A[i]=='1'||B[i]=='1')ans+=(1<<a);
	}
	cout<<ans<<endl;
}