#include <bits/stdc++.h>
//#include <atcoder/all>
//using namespace atcoder;
using namespace std;
const int INF = 1e9;
using ll = long long;
using inv = vector<int>;
using stv = vector<string>;
using pint = pair<int,int>;
#define FOR(i,l,r) for(int i=(l); i<(r); i++)
#define rep(i,r) for(int i=0; i<(r); i++)
#define repl(i,r) for(long long i=0; i<(r); i++)
#define FORl(i,l,r) for(long long i=(l); i<(r); i++)
#define INFL ((1LL<<62)-(1LL<<31))
#define pb(x) push_back(x)
#define CIN(x) cin >> x


int main(){
  string a,b;
  cin >> a >> b;
  unsigned long A = stoul(a, nullptr, 2),B = stoul(b, nullptr, 2);
  cout << (A^B) << endl;
}