#include <fstream>

using namespace std;

ifstream f("cmlsc.in");
ofstream g("cmlsc.out");

int n,i,j,a[1025],b[1025],c[1025],d[1025][1025],lh=0,m;

int main () {
    f >> m >> n;
    for (i=1;i<=m;i++) f >> a[i];
    for (j=1;j<=n;j++) f >> b[j];
    for (i=1;i<=m;i++)
        for (j=1;j<=n;j++)
            if (a[i]==b[j]) d[i][j]=d[i-1][j-1]+1;
                else d[i][j]=max(d[i-1][j],d[i][j-1]);
    i=m;j=n;
    while (i!=0)
        if (a[i]==b[j]) {
            lh++;c[lh]=a[i];
            i--;j--;
        }
        else{
          if (d[i-1][j]<d[i][j-1]) j--;
                              else i--;}
    g << lh << '\n';
    for (i=lh;i>=1;i--)
        g << c[i] << ' ';
    f.close();g.close();
    return 0;
}