#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<n; i++)
#define Sort(vector) sort(vector.begin(), vector.end())
#define Reverse(vector) reverse(vector.begin(), vector.end())
#define RSort(vector) sort(vector.rbegin(), vector.rend())
using ll = long long;
using P = pair<int,int>;
using TU = tuple<int,int,int>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
template<typename T> istream &operator>>(istream &is,vector<T> &v){for(T &in:v){is>>in;}return is;}
template<typename T> ostream &operator<<(ostream &os,vector<T> &v){for(int i=0;i<(int)v.size();i++){os<<v[i]<<" \n"[i==(int)v.size()-1];}return os;}
template<typename T> istream &operator>>(istream &is,vector<vector<T>> &v){for(vector<T> &in:v){is>>in;}return is;}
template<typename T> ostream &operator<<(ostream &os,vector<vector<T>> &v){for(vector<T> &out:v){os<<out;}return os;}




int main(){
  string a,b;cin>>a>>b;

  int anum=0;
  int bnum=0;

  Reverse(a);
  Reverse(b);

  rep(i,a.size()){
    if(a[i]=='1'){
      anum+=(1<<i);
    }
  } 

  
  rep(i,b.size()){
    if(b[i]=='1'){
      bnum+=(1<<i);
    }
  } 

  int res=anum^bnum;
  cout<< res <<'\n';


  return 0;
}