#include<bits/stdc++.h>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))
using namespace std;
using ll = long long;
const ll mod = 998244353;
const vector<int> dx = {1,0,-1,0}, dy = {0,1,0,-1};
using Graph = vector<vector<int>>;

int main(){
  // input
  string a,b; cin >> a >> b;
  // reverse(a.begin(),a.end());
  // reverse(b.begin(),b.end());
  int A = 0, B = 0;
  for (int i=0; i < a.size(); i++){
    A = 2 * A + (a[i] == '1');
  }
  for (int i=0; i < b.size(); i++){
    B = 2 * B + (b[i] == '1');
  }
  cout << (A^B) << endl;
  // solve
  
  // output
  
}