#include<bits/stdc++.h>
using namespace std; 
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define length size()
#define int long long
#define ll long long
int ctoi(const char c){
  switch(c){
    case '0': return 0;
    case '1': return 1;
    case '2': return 2;
    case '3': return 3;
    case '4': return 4;
    case '5': return 5;
    case '6': return 6;
    case '7': return 7;
    case '8': return 8;
    case '9': return 9;
    default : return -1;
  }
}
template<typename T> string join(vector<T> &vec ,const string &sp){
    int si = vec.length;
    if(si==0){
        return "";
    }else{
        stringstream ss;
        rep(i,si-1){
            ss << vec[i] << sp;
        }
        ss << vec[si - 1];
        return ss.str();
    }
}
const int mod = 1000000007;
long long modpow(long long a, long long n, long long mod) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}
int binToUInt(string s){
    int x = 0;
    rep(i,s.size()){
        x *= 2;
        if(s[i] == '1') x++;
    }
    return x;
}
signed main(void){
    string a,b;
    cin >> a >> b;
   // cout << a << b << endl;
    int x = binToUInt(a);
    int y = binToUInt(b);
   // cout << x << y;
    cout << (x^y) << endl;
    return 0;
}