#include <fstream>

using namespace std;

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

int a[1024][1024];
int b[1024], c[1024], sub[1024];
int n, m, i, j, x=0;

int main ()
{
    f >> n >> m;
    for (i=1; i<=n; i++)
        f >> b[i];
    for (i=1; i<=m; i++)
        f >> c[i];
    for (i=1; i<=n; i++)
        for (j=1; j<=m; j++)
        {
            if (b[i] == c[j])
                a[i][j] = a[i-1][j-1]+1;
            else
                a[i][j] = max (a[i-1][j], a[i][j-1]);
        }
    i = n;
    j = m;
    while (a[i][j])
    {
        while (a[i][j] == a[i-1][j])
            i--;
        while (a[i][j] == a[i][j-1])
            j--;
        x++;
        sub[x] = b[i];
        i--;
        j--;
    }
    g << a[n][m] << "\n";
    for (i=x; i>=1; i--)
        g << sub[i] << " ";
    return 0;
}