#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  string S,T;
  cin>>S>>T;
  reverse(S.begin(),S.end());
  reverse(T.begin(),T.end());
  while(S.size() != 40) S += '0';
  while(T.size() != 40) T += '0';
  int ans = 0;
  for(int i=0;i<40;i++){
  	if(S[i]+T[i] == '0'+'1') ans += (1ll<<i);
  }
  cout<<ans<<endl;
}