//
#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rep2(i,start,end) for(int i=(int)start;i<=(int)end;i++)
#define vrep(i, n) for(int i=(int)n-1;i>=0;i--)
#define vrep1(i, n) for(int i=(int)n;i>0;i--)
typedef long long ll;
typedef pair<int,int> pint;
typedef pair<long,long> plong;
typedef vector<int> vint;
typedef vector<long> vlong;

const double pi=M_PI;
const int INF10 = 1000000001;
const long long INF18 = 1e18 + 1;
const int mod = 1000000007;
//const int mod = 998244353;

struct edge{
    edge(int i,long c=1){
        to=i;
        cost=c;
    }
    int to;
    long cost;
};

//bを何回足せばaを超えるか(O(a/b))
//a+b-1/bとすればよし

//2進数表示したときの最高桁(O(log n))
int bi_max(long n){
    int m = 0;
    for (m; (1 << m) <= n; m++);
    m = m - 1;
    return m;
}
//bi_eに二進数表示したやつを代入(O(log^2 n))
//bitset<N> a(n)でnの二進数表示が得られて、a[i]=0or1でi番目のfragが立ってるかわかる
//x^n mod m (nが負の時は０)(O(log n))
long myPow(long x, long n, long m=mod){
    if (n < 0)
        return 0;
    if (n == 0)
        return 1;
    if (n % 2 == 0)
        return myPow(x * x % m, n / 2, m);
    else
        return x * myPow(x, n - 1, m) % m;
}
// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
struct mint{
    ll x; // typedef long long ll;
    mint(ll x = 0) : x((x % mod + mod) % mod) {}
    mint operator-() const { return mint(-x); }
    mint &operator+=(const mint a)
    {
        if ((x += a.x) >= mod)
            x -= mod;
        return *this;
    }
    mint &operator-=(const mint a)
    {
        if ((x += mod - a.x) >= mod)
            x -= mod;
        return *this;
    }
    mint &operator*=(const mint a)
    {
        (x *= a.x) %= mod;
        return *this;
    }
    mint operator+(const mint a) const { return mint(*this) += a; }
    mint operator-(const mint a) const { return mint(*this) -= a; }
    mint operator*(const mint a) const { return mint(*this) *= a; }
    mint pow(ll t) const
    {
        if (!t)
            return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1)
            a *= *this;
        return a;
    }

    // for prime mod
    mint inv() const { return pow(mod - 2); }
    mint &operator/=(const mint a) { return *this *= a.inv(); }
    mint operator/(const mint a) const { return mint(*this) /= a; }
    bool operator!=(const int a) { return this->x!=a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
// combination mod prime
// https://www.youtube.com/watch?v=8uowVvQ_-Mo&feature=youtu.be&t=1619
struct combination{
    vector<mint> fact, ifact;
    combination(int n) : fact(n + 1), ifact(n + 1)
    {
        assert(n < mod);
        fact[0] = 1;
        for (int i = 1; i <= n; ++i)
            fact[i] = fact[i - 1] * i;
        ifact[n] = fact[n].inv();
        for (int i = n; i >= 1; --i)
            ifact[i - 1] = ifact[i] * i;
    }
    mint operator()(int n, int k)
    {
        if (k < 0 || k > n)
            return 0;
        return fact[n] * ifact[k] * ifact[n - k];
    }
};
template<class T>
bool maxin (T &a,T b){if(a<b){a=b;return true;}else return false;};
template<class T>
bool minin (T &a,T b){if(a>b){a=b;return true;}else return false;}
template<class M,class N> 
constexpr common_type_t<M,N> gcd(M a,N b){
    a=abs(a);b=abs(b);
    if(a < b) return gcd(b, a);
    M r;
    while ((r=a%b)) {
        a = b;
        b = r;
    }
    return b;
}
template<class M,class N>
constexpr common_type_t<M,N> lcm(M a,N b){
    return a*b/gcd(a,b);
}

const int N_MAX=4010;
string s[2];
int nxt[2][N_MAX][2];
int n[2],dp[N_MAX][N_MAX];
pair<char,pint> mem[N_MAX][N_MAX];

string solve(){
    int res;
    dp[n[0]][n[1]]=1;
    /*rep(l,2){
        vrep(i,n[l]){
            res=INF10;
            rep(j,2){
                l==0?minin(res,dp[nxt[l][i][j]+1][n[1]]+1):minin(res,dp[n[0]][nxt[l][i][j]+1]+1);
            }
            l==0?dp[i][n[1]]=res:dp[n[0]][i]=res;
        }
    }*/
    vrep(i,n[0]+2){
        vrep(j,n[1]+2){
            if(i==n[0]+1&&j==n[1]+1)continue;
            res=INF10;
            int ni,nj;
            rep(l,2){
                if(i>=n[0])ni=n[0];else ni=nxt[0][i][l];
                if(j>=n[1])nj=n[1];else nj=nxt[1][j][l];
                if(minin(res,dp[ni+1][nj+1]+1)){
                    mem[i][j]={l+'0',{ni+1,nj+1}};
                }
            }
            dp[i][j]=res;
        }
    }
    /*res=dp[0][0];
    rep(i,n[0]+2){
        rep(j,n[1]+2){
            cout<<"("<<i<<","<<j<<")="<<dp[i][j]<<" ";
        }
        cout <<endl;
    }*/
    pint now={0,0};
    string ans="";
    rep(j,dp[0][0]){
        pair<char,pint> nt;
        //bool tof=false;
        /*rep(i,2){
            nx=nxt[0][now.first][i]+1;
            ny=nxt[1][now.second][i]+1;
            cout << dp[nx][ny]+1<<" "<<res-j <<endl;
            if(dp[nx][ny]+1==res-j){
                ans.push_back(i+'0');
                tof=true;
                break;
            }
        }*/
        nt=mem[now.first][now.second];
        now=nt.second;
        ans+=nt.first;
        //cout << "nx="<<now.first<<" ny="<<now.second <<endl;
        /*if(!tof){
            cout << "!!!???" <<endl;
        }*/
        //now={nx,ny};
    }
    return ans;
}

int main(){
    int x,y;
    //入力
    cin>>s[0];
    cin>>s[1];
    //処理
    rep(i,2){
        n[i]=s[i].size();
        rep(l,n[i]+1){
            rep(j,2){
                nxt[i][l][j]=n[i];
            }
        }
        vrep(j,n[i]){
            rep(l,2)nxt[i][j][l]=nxt[i][j+1][l];
            nxt[i][j][s[i][j]-'0']=j;
        }
    }
    string ans=solve();
    //出力
    cout << ans <<endl;
}


Measured memory_bytes: 253904