#include <fstream>

using namespace std;

int main()
{
    int m,n,a[1025],b[1025],i,j,v[1025][1025]={0},k=1,sol[1025];
    ifstream f ("cmlsc.in");
    ofstream g ("cmlsc.out");
    f>>m>>n;
    for (i=1;i<=m;i++)
        f>>a[i];
    for (i=1;i<=n;i++)
        f>>b[i];
    for (i=1;i<=m;i++)
        for (j=1;j<=n;j++)
            if (a[i]==b[j])
                v[i][j]=v[i-1][j-1]+1;
            else
                if (v[i-1][j]>=v[i][j-1])
                    v[i][j]=v[i-1][j];
                else
                    v[i][j]=v[i][j-1];
    for (i=m , j=n;i>=1 && j>=1;)
    {
        if (a[i]==b[j])
        {
            sol[k]=a[i];
            k++;
            i--;
            j--;
        }
        else
        if (v[i-1][j]<v[i][j-1])
            j--;
            else
                i--;
    }
    g<<v[m][n]<<endl;
    for (i=k-1;i>=1;i--)
        g<<sol[i]<<" ";
    f.close ();
    g.close ();
    return 0;
}