#include<bits/stdc++.h>
using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  string a, b;
  cin >> a >> b;
  long long ans = 0, two = 1;
  reverse(a.begin(), a.end());
  reverse(b.begin(), b.end());
  for (int i = 0; i < 50; i++) {
    if (i >= a.size() && i >= b.size()) break;
    else if (i >= a.size()) {
      if (b[i] == '1') ans += two; 
    } else if (i >= b.size()) {
      if (a[i] == '1') ans += two;
    } else {
      if (!(a[i] == b[i])) ans += two;
    }
    two *= 2;
  }
  cout << ans << endl;
  return 0;
}