#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
//#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
template<int MOD> struct ModInt {
    static const int Mod = MOD; unsigned x; ModInt() : x(0) { }
    ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    int get() const { return (int)x; }
    ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
    ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
    ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
    ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
    ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
    ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
    ModInt inverse() const {
        long long a = x, b = MOD, u = 1, v = 0;
        while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); }
        return ModInt(u);
    }
    bool operator==(ModInt that) const { return x == that.x; }
    bool operator!=(ModInt that) const { return x != that.x; }
    ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }
};
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
    ModInt<MOD> r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r;
}
int getrand(int L, int R) { // [L,R]
    random_device rd; mt19937 mt(rd()); uniform_int_distribution<> rand(L, R); return rand(mt);
}
typedef ModInt<1000000007> mint1;
typedef ModInt<1000000009> mint2;
int primes[10] = { 10007, 10009, 10037, 10039, 10061, 10067, 10069, 10079, 10091, 10093 };
bool isShuffle = false;
struct RollingHash {
    mint1 p1; mint2 p2;
    int n;
    vector<mint1> m1; vector<mint2> m2;
    vector<mint1> v1; vector<mint2> v2;

    RollingHash() {
        if (!isShuffle) {
            rep(i, 0, 101) { int a = getrand(0, 9); int b = getrand(0, 9); swap(primes[a], primes[b]); }
            isShuffle = true;
        }
        p1 = primes[0], p2 = primes[1];
    }

    void init(string s, char o = 'a') {
        vector<int> v;
        fore(c, s) v.push_back(c - o);
        init(v);
    }

    void init(vector<int> s) {
        n = s.size();
        m1.resize(n); m2.resize(n); v1.resize(n); v2.resize(n);

        m1[0] = 1; m2[0] = 1;
        v1[0] = s[0]; v2[0] = s[0];

        rep(i, 1, n) {
            m1[i] = m1[i - 1] * p1;
            m2[i] = m2[i - 1] * p2;
            v1[i] = v1[i - 1] + m1[i] * s[i];
            v2[i] = v2[i - 1] + m2[i] * s[i];
        }
    }
    inline pair<mint1, mint2> hash(int l, int r) { // s[l..r]
        assert(l <= r); assert(r < n);
        mint1 a = v1[r];
        if (l) a -= v1[l - 1];
        a *= m1[n - 1 - r];

        mint2 b = v2[r];
        if (l) b -= v2[l - 1];
        b *= m2[n - 1 - r];

        return { a, b };
    }
};
#define TOP_CHAR 'a'
struct StringMaster {
    string S, SR; int N;
    vector<int> nxt[26], bak[26];
    RollingHash rs, rsr;
    StringMaster() {}
    StringMaster(string s) { init(s); }
    void init(string s) {
        S = s; SR = s; reverse(all(SR)); rs.init(S); rsr.init(SR); N = S.length();

        rep(c, 0, 26) { nxt[c].resize(N); bak[c].resize(N); }
        
        rep(c, 0, 26) rep(i, 0, N) nxt[c][i] = N;
        rep(i, 0, N) nxt[S[i] - TOP_CHAR][i] = i;
        rep(c, 0, 26) rrep(i, N - 2, 0) chmin(nxt[c][i], nxt[c][i + 1]);

        rep(c, 0, 26) rep(i, 0, N) bak[c][i] = -1;
        rep(i, 0, N) bak[S[i] - TOP_CHAR][i] = i;
        rep(c, 0, 26) rep(i, 1, N) chmin(bak[c][i], bak[c][i - 1]);
    }
    int getMaxSame(int l, int r) { // [l-n+1,l]^-1 = [r,r+n-1] and n is maximum
        int lsz = l + 1;
        int rsz = N - r;

        int ok = 0, ng = min(lsz, rsz) + 1;
        while (ok + 1 != ng) {
            int md = (ok + ng) / 2;
            if (rs.hash(r, r + md - 1) == rsr.hash(N - 1 - l, N - 1 - l + md - 1)) ok = md;
            else ng = md;
        }
        return ok;
    }
    int getNext(int cu, char c) {
        if (cu == N) return N;
        return nxt[c - TOP_CHAR][cu];
    }
    int getBack(int cu, char c) {
        if (cu < 0) return -1;
        return bak[c - TOP_CHAR][cu];
    }
};
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧  
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     
　　　　／　　　＼　 　  |　|     
　　　 /　　 /￣￣￣￣/　　|  
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿  
　 　　　＼/＿＿＿＿/　（u　⊃  
---------------------------------------------------------------------------------------------------*/











string S, T;
int NS, NT;
int dp[3010][3010];
tuple<int, int, char> pre[3010][3010];
//---------------------------------------------------------------------------------------------------
void _main() {
    cin >> S >> T;
    NS = S.length(), NT = T.length();

    StringMaster SMS(S);
    StringMaster SMT(T);

    rep(s, 0, NS) rep(t, 0, NT) rep(c, 0, 26) {
        int ss = SMS.getNext(s, char('a' + c));
        int tt = SMT.getNext(t, char('a' + c));

        if (ss < NS and tt < NT) {
            if (chmax(dp[ss + 1][tt + 1], dp[s][t] + 1)) {
                pre[ss + 1][tt + 1] = make_tuple( s, t, char('a'+c) );
            }
        }
    }

    int ma = 0;
    rep(s, 0, NS + 1) rep(t, 0, NT + 1) chmax(ma, dp[s][t]);

    rep(s, 0, NS + 1) rep(t, 0, NT + 1) if (dp[s][t] == ma) {
        string ans = "";
        while (s != 0 and t != 0) {
            int ss, tt; char cc;
            tie(ss, tt, cc) = pre[s][t];
            ans += cc;
            s = ss, t = tt;
        }
        reverse(all(ans));
        cout << ans << endl;
        return;
    }

}


Measured memory_bytes: 143104