#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

//ifstream fin("cmlsc.in");
//#define cin fin

struct matrix
{
    int a;
    short h;
};

matrix a[1025][1025];
vector<int>x,y;

vector<int> o;

void back(int f, int g)
{
        if(x[f]==y[g])o.push_back(x[f]);
        if(a[f][g].h==1) back(f-1,g);
        if(a[f][g].h==2) back(f,g-1);
        if(a[f][g].h==3) back(f-1,g-1);
}

int main()
{
    int n,m;
    cin>>n>>m;
    int i,j;
    x.resize(n);
    y.resize(m);
    for(i=1;i<=n;i++)
        cin>>x[i];
    for(j=1;j<=m;j++)
        cin>>y[j];

    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(x[i]==y[j])
            {
                a[i][j].a=a[i-1][j-1].a+1;
                a[i][j].h=3;
            }
            else
            {
                if(a[i-1][j].a>a[i][j-1].a)
                {
                    a[i][j].a=a[i-1][j].a;
                    a[i][j].h=1;
                }
                else
                {
                    a[i][j].a=a[i][j-1].a;
                    a[i][j].h=2;
                }
            }
        }
    }

    /*for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            cout<<a[i][j].a<<" ";
        }
        cout<<"\n";
    }*/


    back(n,m);
    cout<<o.size()<<"\n";
    for(auto it=o.rbegin();it!=o.rend();it++) cout<<*it<<" ";

    return 0;
}