#include <fstream>



using namespace std;



ifstream f("cmlsc.in");

ofstream g("cmlsc.out");



int pd[1025][1025], n, m, a[1025], b[1025], sol[1025], k;



void citire() {

    f >> n >> m;

    for(int i = 1; i <= n; ++i)

        f >> a[i];

    for(int j = 1; j <= m; ++j)

        f >> b[j];

}



void rezolva() {

    for(int i = 1; i <= m; ++i)

        for(int j = 1; j <= n; ++j)

            if(b[i] == a[j])

                pd[i][j] = pd[i-1][j-1] + 1;

            else

                pd[i][j] = max(pd[i-1][j], pd[i][j-1]);

}



void cmf() {

    for(int i = m, j = n; i;)

        if(b[i] == a[j])

            sol[++k] = a[j], i--, j--;

        else

            if(pd[i-1][j] < pd[i][j-1])

            --j;

        else

            --i;

}



void afisare() {

    g << k << '\n';

    for(int i = k; i > 0; --i)

        g << sol[i] << ' ';

}



int main()

{

    citire();

    rezolva();

    cmf();

    afisare();

    f.close();

    g.close();

    return 0;

}