#include <bits/stdc++.h>

using namespace std;

ifstream f("cmlsc.in");
ofstream g("cmlsc.out");

int a[1024] , b[1024] , c[1024][1024] , d[10001] , n , m , p;

int main()
{
    f >> n >> m;

    for ( int i = 1 ; i <= n ; i++)
        f >> a[i];

    for ( int i = 1 ; i <= m ; i++)
        f >> 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
                c[i][j] = max(c[i - 1][j] , c[i][j - 1]);
        }
    }

    p = 0;

    for ( int i = n , j = m ; i > 0 ; )
    {
        if( a[i] == b[j])
            d[p++] = a[i] , i-- , j--;
        else
            if(c[i - 1][j] < c[i][j - 1])
            j--;
        else
            i--;
    }
    g << p << '\n';
    for ( int i = p - 1 ; i >= 0 ; i--)
        g << d[i] << " ";
}