#include <iostream>
#include <fstream>
using namespace std;

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

int M, N, i, a[1025], b[1025], c[1025], D[1025][1025], bst = 0, j;

int main()
{
    f >> M>>N;
    for (i = 1;i <= M;i++)
        f >> a[i];
    for (i = 1;i <= N;i++)
        f >> b[i];
    for (i = 1;i <= M;i++)
        for (j = 1;j <= N;j++)
        {
            if (a[i] == b[j])
                D[i][j] = 1 + D[i - 1][j - 1];
            else
                D[i][j] = (D[i - 1][j] > D[i][j - 1]) ? D[i - 1][j] : D[i][j - 1];
        }
    i = M;
    j = N;
    while (i >= 1 && j >= 1)
    {
        if (a[i] == b[j])
        {
            c[bst] = a[i];
            bst++;
            i--;
            j--;
        }
        else
        {
            if (D[i - 1][j] < D[i][j - 1])
                j--;
            else
                i--;
        }
    }
    g << bst << endl;
    for (i = bst-1;i >= 0;i--)
        g << c[i] << " ";
}