#include <bits/stdc++.h>
#define Nmax 1026
using namespace std;
ifstream fin ("cmlsc.in");
ofstream fout ("cmlsc.out");

int a[ Nmax ][ Nmax ];

int n,m, maxim;

vector < char >  v1, v2, sol;

void citesc ();
void process();
void afisare ();

int main()
{
    citesc();
    process();
    afisare();
}

void process()
{
    bool k = 0;

    for ( int j = 0; j < m; j++ )
    {
        if ( v1[0] == v2[j] )
            k = 1 , sol.push_back(v1[0]), maxim = 1;

        a[1][1+j] = k;
    }

    for ( int i = 2; i <= n; i++ )
        for ( int j = 1; j <= m; j++ )
        {
             if ( v1[i-1] == v2[j-1] )
                {
                    a[i][j] = a[i-1][j-1]+1;
                    if ( a[i][j] > maxim )
                    {
                        maxim = a[i][j];
                        sol.push_back(v1[i-1]);
                    }
                }
            else
                a[i][j]= max (a[i-1][j],a[i][j-1]);
        }
}

void citesc ()
{
    int x;

    fin >> n >> m;

    v1.reserve ( n+2 );
    v2.reserve ( m+2 );

    sol.reserve( min(n,m) + 2 );

    for  ( int i = 0; i < n; i++ )
    {
        fin >> x;

        v1.push_back(x);
    }

    for  ( int i = 0; i < m; i++ )
    {
        fin >> x;

        v2.push_back(x);
    }

    fin.close();
}

void afisare ()
{
    fout << maxim << '\n';

    int lng = sol.size();

    for ( int i = 0; i < lng; i++ )
        fout << int(sol[i]) << ' ';

    fout.close();
}