#include <fstream>
#include <cmath>
#include <algorithm>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int a[1025][1025],b[1025],c[1025],sub[1025];
int main()
{
    int n,m,i,j,x=0;
    f>>n>>m;
    for(i=1;i<=n;i++)
    f>>b[i];
    for(i=1;i<=n;i++)
    f>>c[i];
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    {
        if(b[i]==c[j])
        a[i][j]=a[i-1][j-1]+1;
        else
        a[i][j]=max(a[i-1][j],a[i][j-1]);
    }
    /*for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        g<<a[i][j]<<" ";
        g<<"\n";
    }
    g<<"\n";
    */i=n;j=m;
    while(a[i][j])
    {
        while(a[i][j]==a[i-1][j])
        i--;
        while(a[i][j]==a[i][j-1])
        j--;
        x++;
        sub[x]=b[i];
        i--;
        j--;
    }
    g<<a[n][m]<<"\n";
    for(i=x;i>=1;i--)
    g<<sub[i]<<" ";
    return 0;
}