#include <iostream>
#include <fstream>

using namespace std;

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

short a[1030], b[1030], c[1030];
short l[1030][1030];

int main()
{
    int n, m, k = 1;
    fin >> n >> m;
    for (int i = 1; i <= n; i++)
        fin >> a[i];
    for (int j = 1; j <= m; j++)
        fin >> b[j];
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
        {
            if (a[i] == b[j])
                l[i][j] = l[i - 1][j - 1] + 1;
            else
                l[i][j] = max(l[i - 1][j], l[i][j - 1]);
        }
    fout << l[n][m] << '\n';
    int i = n, j = m;
    while (i > 0 && j > 0)
    {
        if (l[i][j] == l[i - 1][j])
            i--;
        else if (l[i][j] == l[i][j - 1])
            j--;
        else
        {
            c[k] = a[i];
            k++;
            i--;
            j--;
        }
    }
    for (int i = k - 1; i >= 1; i--)
        fout << c[i] << ' ';
    fout << '\n';
    return 0;
}