#include<iostream>
#include<fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int n,m,a[1025],b[1025],d[1025][1025],rasp[1025];
int main()
{
    f>>n>>m;
    for(int i=1;i<=n;i++)
    {
        f>>a[i];
    }
    for(int i=1;i<=m;i++)
        f>>b[i];
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            if(a[i] == b[j])
                d[i][j] = d[i - 1][j - 1] + 1;
            else
                d[i][j] = max(d[i][j - 1],d[i - 1][j]);
    g<< d[n][m]<<"\n";
    int i = n;
    int j = m;
    int k = d[n][m];
    while(i > 0 && j > 0)
    {
        if(a[i] == b[j])
        {
            rasp[k] = a[i];
            k--;
            i--;
            j--;
        }
        else
        {
            if(d[i][j-1]>d[i-1][j])
            {
                j--;
            }
            else
            {
                i--;
            }
        }

    }
    for(int i=1;i<=d[n][m];i++)
        g<<rasp[i]<<" ";
}