#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int c[1025][1025],a[1025],b[1025],v[1025],n,m;
int main()
{
    fin>>n>>m;
    for(int i=1;i<=n;i++)
        fin>>a[i];
    for(int i=1;i<=m;i++)
        fin>>b[i];
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
            if(a[i]==b[j])
            c[i][j]=c[i-1][j-1]+1;
            else
            if(c[i][j-1]>=c[i-1][j])
                c[i][j]=c[i][j-1];
            else
                c[i][j]=c[i-1][j];
        }

        fout<<c[n][m]<<'\n';

        int i=n,j=m,q=1;

        while((i>=0 and j>=0) and c[i][j]!=0)
        {
            if(a[i]==b[j])
            {
                v[q]=a[i];
                q++;
                i--;
                j--;
            }
            else if(c[i-1][j]>c[i][j-1])i--;
            else j--;

        }

            fout<<v[i]<<" ";
    return 0;
}