#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(int i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
template<typename T> bool chmax(T& x, const T& y){return (x<y)?(x=y,true):false;};
template<typename T> bool chmin(T& x, const T& y){return (x>y)?(x=y,true):false;};
constexpr ll MOD=998244353;
constexpr ll INF=2e18;

int main(){
    string a, b; cin >> a >> b;
    reverse(ALL(a));
    reverse(ALL(b));
    while(a.size()<30) a+='0';
    while(b.size()<30) b+='0';
    int ans=0;
    REP(i,30){
        if(a[i]!=b[i])
            ans+=1<<i;
    }
    cout << ans << endl;
    return 0;
}