#include <iostream>
#include <fstream>
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
int a[1024], b[1024];
int dp[1025][1025];
void afisareMatrice(int m, int n)
{
    for(int i = 0; i < m; i++)
    {
        for(int j = 0; j < n; j++)
        {
            cout<<dp[i][j]<<" ";
        }
        cout<<endl;
    }
    cout<<endl;
}
void subsir(int m, int n)
{
    if(m == 0 || n == 0)
    {
        return;
    }
    if(a[m-1] == b[n-1])
    {
        subsir(m-1, n-1);
        out<<a[m-1]<<" ";
    }
    else
    {
        if(dp[m-1][n] > dp[m][n-1])
        {
            subsir(m-1, n);
        }
        else
        {
            subsir(m, n-1);
        }
    }
}
int main()
{
    int m, n;
    in >> m >> n;
    for(int i = 0; i < m; i++)
    {
        in >> a[i];
    }
    for(int i = 0; i < n; i++)
    {
        in >> b[i];
    }
    in.close();
    m++;
    n++;
    for(int i = 1; i < m; i++)
    {
        for(int j = 1; j < n; j++)
        {
            if(a[i-1] == b[j-1])
            {
                dp[i][j] = 1 + dp[i-1][j-1];
            }
            else
            {
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            }
        }
    }
    //afisareMatrice(m, n);
    out<<dp[m-1][n-1]<<endl;
    subsir(m-1, n-1);
    out.close();
    return 0;
}