#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i, n) for (int i=0; i<(n); i++)
#define len(x) (int)(x).size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using namespace std;
using namespace atcoder;
using ll = long long;
using mint9 = atcoder::modint998244353;
using mint10 = atcoder::modint1000000007;

int main() {
   ios::sync_with_stdio(false);
   cin.tie(0);

   string A, B;
   cin >> A >> B;
   int N = max(len(A), len(B));
   vector<int> ans(N);
   A = string(N-len(A), '0') + A;
   B = string(N-len(B), '0') + B;

   rep(i, N) {
      ans[i] = (A[i]==B[i]? 0:1);
   }
   int ret = 0;
   int d = 1;
   rep(i, N) {ret += d * ans[N-i-1]; d*=2;}
   cout << ret << endl;
   return 0;
}