// 1
// 2
// 3
// 4

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>

using namespace std;

// Í.Î.Ï.

#define forn(i, n) for (int i = 0; i < (int)(n); i++)

const int N = (int)1e3;

char s[N + 1], t[N + 1];
int sn, tn;

int f[N + 2][N + 2];
string ans[N + 2][N + 2];

inline void relax( int i, int j, int b, const string &s )
{
  if (f[i][j] < b)
    f[i][j] = b, ans[i][j] = s;
}

void solve()
{
  memset(f, 0, sizeof(f));
  forn(i, sn + 1) // i = 0..sn
    forn(j, tn + 1) // j = 0..tn
    {
      if (s[i] == t[j])
        relax(i + 1, j + 1, f[i][j] + 1, ans[i][j] + s[i]);
      relax(i + 1, j, f[i][j], ans[i][j]);
      relax(i, j + 1, f[i][j], ans[i][j]);
    }

  printf("%d\n", f[sn][tn]);
  printf("%s\n", ans[sn][tn].c_str());
}

int main()
{
  gets(s);
  gets(t);
  sn = strlen(s);
  tn = strlen(t);
  solve();
  return 0;
}