#include <bits/stdc++.h>
#include "atcoder/modint"

using i64 = long long;
using Fp = atcoder::modint998244353;

int main() {
    std::string A, B;
    std::cin >> A >> B;
    int a = 0, b = 0;
    for (int i = 0; i < (int)A.size(); ++i) if (A[i] == '1') a |= (1 << (A.size() - i - 1));
    for (int i = 0; i < (int)B.size(); ++i) if (B[i] == '1') b |= (1 << (B.size() - i - 1));
    std::cout << (a xor b) << std::endl;
}