#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;
}