#include <bits/stdc++.h>
using namespace std;
int main() {
  string A, B;
  cin >> A >> B;
  int N = max(A.size(), B.size());
  reverse(A.begin(), A.end());
  reverse(B.begin(), B.end());
  int c = 0;
  
  for(int i=0; i<N; i++){
    c += pow(10, i);
    if(A[i]=='1' && B[i]=='1'){
      c -= pow(10, i);
    }else if(A[i]=='0' && B[i]=='0'){
      c -= pow(10, i);
    }
  }
  
  int de = 0;
  int ba = 1;
  while(c>0){
    de = de + (c%10) * ba;
    c = c/10;
    ba = ba*2;
  }
  cout << de << endl;
}