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

int main() {
  string a, b;
  cin >> a >> b;
  if (b.size() > a.size())
    swap(a, b);
  for (int i = 0; i < a.size() - b.size(); i++) {
    b = "0" + b;
  }

  
  string c = "";
  for (int i = 0; i < a.size(); i++) {
    if (a[i] != b[i]) 
      c += "1";
    else
      c += "0";
  }

  reverse(c.begin(), c.end());
  int ans = 0;
  for (int i = 0; i < c.size(); i++) {
    if (c[i] == '1')
      ans += pow(2, i);
  }
  cout << ans << '\n';
  return 0;
}