#include <fstream>

using namespace std;
short m[1025][1025];

int main()
{
    ifstream f("cmlsc.in");
    ofstream g("cmlsc.out");
    short n, m, i, j, *v1, *v2, *sol, idx=0;
    f >> n >> m;
    v1 = new int[n];
    v2 = new int[m];
    sol = new int[n];
    for (i=0;i<n;i++)
        f>>v1[i];
    for (i=0;i<m;i++)
        f>>v2[i];
    for (i=1;i<=n;i++)
        for (j=1;j<=m;j++)
            if (v1[i-1]==v2[j-1])
                D[i][j]+=(D[i-1][j-1])+1;
            else
                if (D[i-1][j] > D[i][j-1])
                    D[i][j] = D[i-1][j];
                else
                    D[i][j] = D[i[i][j-1];
    for (i=n, j=m; i;)
        if (v1[i-1] == v2[j-1])
            sir[idx++] = v1[i-1], --i, --j;
        else if (m[i-1][j] < m[i][j-1])
            --j;
        else
            --i;
    g << idx << '\n';
    for (i=0;i<idx;i++)
        g << sir[i] << ' ';
    return 0;
}