/* author: kyawa */ #include<bits/stdc++.h> using namespace std; /* 考察 */ int main(){ string A, B; cin >> A >> B; reverse(A.begin(), A.end()); reverse(B.begin(), B.end()); A.resize(60, '0'); B.resize(60, '0'); int64_t res = 0; for(int64_t i = 0; i < 60; i++){ res += (1<<i) * ((A[i] - '0')^(B[i] - '0')); } cout << res << '\n'; }