#include <fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int a[1025][1025],b[1025],c[1025],sub[1025];
int main()
{  int n,m,i,j,x=0;
   f>>n>>m;
   for(i=1; i<=n; i++)
      f>>b[i];
   for(i=1; i<=m; i++)
      f>>c[i];
   for(i=1; i<=n; i++)
      for(j=1; j<=m; j++)
      {  if(b[i]==c[j])
            a[i][j]=a[i-1][j-1]+1;
         else
            a[i][j]=max(a[i-1][j], a[i][j-1]);
      }
   i=n;
   j=m;
   while(a[i][j])
   {  while(a[i][j]==a[i-1][j])
         i--;
      while(a[i][j]==a[i][j-1])
         j--;

      x++;
      sub[x]=b[i];
      i--;
      j--;
   }
   g<<a[n][m]<<"\n";
   for(i=x; i>=1; i--)
      g<<sub[i]<<" ";
   return 0;
}