#include <fstream>

using namespace std;

ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

const int Nmax=1030;

int n,m,d[Nmax][Nmax],a[Nmax],b[Nmax],sol[Nmax],best,k=1;

int maxim ( int x , int y ){
    if ( x > y )
        return x;
    return y;
}

void afisare ( int x , int y ){
    if ( x == 0 || y == 0 )
        return;

    if ( a[x] == b[y] ){
        afisare(x-1,y-1);
        fout<<a[x]<<' ';
        return;
    }
    if ( d[x-1][y] > d[x][y-1] )
        afisare(x-1,y);
    else
        afisare(x,y-1);


}

int main()
{
    fin>>n>>m;
    for ( int i=1 ; i<=n ; i++ )
        fin>>a[i];
    for ( int i=1 ; i<=m ; i++ )
        fin>>b[i];
    for ( int i=1 ; i<=n ; i++ ){
        for ( int j=1 ; j<=m ; j++ ){
            if ( a[i] == b[j] )
                d[i][j]=d[i-1][j-1]+1;
            else
                d[i][j]=maxim(d[i-1][j],d[i][j-1]);
            if ( d[i][j] > best )
                best=d[i][j];
        }
    }
    fout<<d[n][m]<<'\n';
    afisare(n,m);
}