#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
#include <set>
#include <queue>
#include <iomanip>
#include <cstring>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i,n) for (int i = 0; i < int(n);i++)

int main(){
  string s,t;
  cin >> s >> t;
  int a = 0,b = 0;
  reverse(s.begin(),s.end());
  reverse(t.begin(),t.end());
  int cur = 1;
  for (int i = 0; i < s.size();i++){
    if (s[i] == '1'){
      a += cur;
    }
    cur <<=1;
  }
  cur = 1;
  for (int i = 0; i < t.size();i++){
    if (t[i] == '1'){
      b += cur;
    }
    cur <<=1;
  }
  cout << (a^b) << endl;
  
  return 0;
}