#include <iostream>

int main() {
  using namespace std;
  ios_base::sync_with_stdio(false);

  string retezec_a, retezec_b;

  cin >> retezec_a >> retezec_b;

  int delka_a = retezec_a.length();
  int delka_b = retezec_b.length();
  int nsp_tabulka[delka_a+1][delka_b+1];

  for (int a=0; a<=delka_a; ++a)
    for (int b=0; b<=delka_b; ++b)
      nsp_tabulka[a][b] = 0;

  for (int a=1; a<=delka_a; ++a) {
    for (int b=1; b<=delka_b; ++b) {
      nsp_tabulka[a][b] = max(max(nsp_tabulka[a-1][b], nsp_tabulka[a][b-1]),
                              nsp_tabulka[a-1][b-1] + (retezec_a[a-1] == retezec_b[b-1] ? 1 : 0));
    }
  }

  int delka_nsp = nsp_tabulka[delka_a][delka_b];

  string nsp(delka_nsp, '-');
  int a = delka_a;
  int b = delka_b;
  int i_nsp = delka_nsp - 1;

  while (a > 0 && b > 0) {
    if (nsp_tabulka[a][b] == nsp_tabulka[a-1][b-1] + 1) {
      nsp[i_nsp--] = retezec_a[a-1];
      a--; b--;
    }
    else {
      if (nsp_tabulka[a][b] == nsp_tabulka[a-1][b]) {
        a--; continue;
      }
      if (nsp_tabulka[a][b] == nsp_tabulka[a][b-1]) {
        b--; continue;
      }
      a--; b--;
    }
  }

  a = 0;
  b = 0;
  i_nsp = 0;

  string nsn(delka_a+delka_b-delka_nsp, '-');
  int i_nsn = 0;

  while (a < delka_a && b < delka_b) {
    while (retezec_a[a] != nsp[i_nsp]) {
      nsn[i_nsn++] = retezec_a[a++];
    }
    while (retezec_b[b] != nsp[i_nsp]) {
      nsn[i_nsn++] = retezec_b[b++];
    }
    a++;
    b++;
    nsn[i_nsn++] = nsp[i_nsp++];
  }

  while (a < delka_a) {
    nsn[i_nsn++] = retezec_a[a++];
  }

  while (b < delka_b) {
    nsn[i_nsn++] = retezec_b[b++];
  }

  cout << nsn;

  return 0;
}