#include <iostream>
#include <fstream>
#include <vector>

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

int mat[1025][1025];
int sir1[1025],sir2[1025];
vector <int> sub;

int main()
{
    int m,n;

    f>>m;
    f>>n;

    for (int i=1; i<=m; i++)
    {
        f>>sir1[i];
    }

    for (int i=1; i<=n; i++)
    {
        f>>sir2[i];
    }

    for (int i=1; i<=m; i++)
    {
        for (int j=1; j<=n; j++)
        {
            if (sir1[i]==sir2[j])
                {
                    mat[i][j]=mat[i-1][j-1]+1;
                }
            else
                mat[i][j]=max(mat[i-1][j],mat[i][j-1]);
        }
    }

    int i=m;
    int j=n;
    while(i>=0&&j>=0)
    {
        if(sir1[i]==sir2[j])
        {
            sub.push_back(sir1[i]);
            i--;
            j--;
        }
        else if(mat[i-1][j]<=mat[i][j-1])
            j--;
        else
            i--;
    }

    g<<sub.size()<<'\n';

    for (int i=sub.size()-1; i>=0;i--)
    {
        g<<sub[i]<<" ";
    }
    f.close();
    g.close();
    return 0;
}