using namespace std;
#include <fstream>
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

const int Mmax = 1024;
const int Nmax = 1024;

int a[Mmax+5], b[Nmax+5], sir[Nmax+5];
int best[Mmax+5][Nmax+5];


int main()
{
    int i, j, m, n, lg;
    fin >> m >> n;
    for(i = 1; i <= m; ++i) fin >> a[i];
    for(i = 1; i <= n; ++i) fin >> b[i];

    for(i = 1; i <= m; ++i)
        for(j = 1; j <= n; j++)
        {
            if(a[i] == b[j]) best[i][j] = 1 + best[i-1][j-1];
            else
            {
                if(best[i-1][j] < best[i][j-1]) best[i][j] = best[i][j-1];
                else best[i][j] = best[i-1][j];
            }
        }

    fout << best[m][n] << '\n';

    for(i = m, j = n, lg = 0; i && j; )
    {
        if(a[i] == b[j]) sir[lg] = a[i], ++lg, --i, --j;
        else
        {
            if(best[i-1][j] <= best[i][j-1]) --j;
            else --i;
        }
    }
    for(i = lg-1; i >= 0; --i) fout << sir[i] << ' ';
    fout << '\n';
    return 0;
}