#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pint = pair<int,int>;


int main()
{
    string A, B;
    cin >> A >> B;
    int a = 0, b = 0;
    reverse(A.begin(), A.end());
    reverse(B.begin(), B.end());

    for(int i = 0; i < (int)A.size(); i++) {
        a += (1<<i) * (A[i] - '0');
    }


    for(int i = 0; i < (int)B.size(); i++) {
        b += (1<<i) * (B[i] - '0');
    }

    cout << (a xor b) << endl;
    


}