#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
using namespace std;

int main(){
    int x, y;
    string a, b;
    cin >> a >> b;
    x = stoi(a, nullptr, 2);
    y = stoi(b, nullptr, 2);
    cout << (x^y) << endl;
    /*
    cout << x << endl << y << endl;
    cout << (x^y) << endl << (x&&y) << endl; //ビット演算
    */
}