#include <iostream>
#include <string>
#include <cmath>
#define rep(i,j,n) for(int i=j;i<n;i++)
using ll = long long; 
using namespace std;
//vector<int> DX={0,1,0,-1,0,1,-1,-1,1};
//vector<int> DY={0,0,1,0,-1,1,1,-1,-1};

int toten(const string& ans) {
    int nans = 0;
    int size = ans.size();

    for (int i = 0; i < size; ++i) {
        if (ans[i] == '1') {
            int plus = size - i - 1;
            nans += pow(2, plus);
        }
    }

    return nans;
}


int main(){
    string A,B; cin >> A >> B;
    string ans;

    bool upto=false;
    int N=A.size(),N2=B.size();
    while(N<N2){
        A='0' + A;
        N++;
    }
    while(N>N2){
        B='0' + B;
        N2++;
    }

    rep(i,0,N){
        if(!upto){
            int k=(A[i]-'0'+B[i]-'0')%2;
            if(k==0)continue;
            else {
                ans+=(k+'0');
                upto=true;
            }
        }
        else {
            int k=(A[i]-'0'+B[i]-'0')%2;
            ans+=(k+'0');
        }
    }


    cout << toten(ans) << endl;
}