#include <iostream>
#include<fstream>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int main()
{
    int m, n, i, j, k, x;
    int a[1024], b[1024], c[1024][1024] = {0}, sir[1024];
    x=0;
    fin >> m >> n;
    for (i=1; i<=m; i++)
        fin >> a[i];
    for (i=1; i<=n; i++)
        fin >> b[i];
    for (i=1; i<=m; i++)
        for (j=1; j<=n; j++)
        {
            if (a[i]==b[j])
                c[i][j]=c[i-1][j-1]+1;
            else
            {
                if (c[i-1][j] > c[i][j-1])
                    c[i][j] = c[i-1][j];
                else
                    c[i][j] = c[i][j-1];
            }
        }
    i=m;
    j=n;
    while (i>0 && j>0)
    {
        if (a[i]==b[j])
        {
            sir[x++]=a[i];
            i--;
            j--;
        }
        else
            if (c[i-1][j]<c[i][j-1])
                j--;
            else
                i--;
    }
    fout << x << '\n';
    for (k=x; k>=1; k--)
        fout << sir[k] << ' ';
}