#include <bits/stdc++.h>
using namespace std;
using ll= long long;
using ull=unsigned long long;
using ldo =long double;
#define rep(i,n,k) for(ll i = k; i < (ll)(n); i++)
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
const ll INF = 1e18;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;

int main() {
  string A,B,C="";
  cin>>A;
  cin>>B;
  rep(i,max(A.size(),B.size())+1,1){
    if(A.size()-i<0)C.push_back(B[A.size()-i]);
    else if(B.size()-i<0)C.push_back(A[B.size()-i]);
    else{
      if((A[A.size()-i]==B[B.size()-i])and(A[A.size()-i]=='1')){
        C.push_back('0');
      }else if((A[A.size()-i]=='1')or('1'==B[B.size()-i])){
        C.push_back('1');
      }else{
        C.push_back('0');
      }
    }
    
  }
  ll a=0,now=1;
  rep(i,C.size(),0){
    if(C[i]=='1')a+=now;
    now*=2;
  }
  cout<<a<<endl;
  return 0;
}