#include <fstream>

using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int b[1025], c[1025], m, n, i, j,x=0, a[1025][1025], sub[1025];

int main()
{
   f >> n >> m;
    for( i = 1; i<=n ; i++)
        f >> b[i];
    for( i = 1 ; i <=m ; 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]);
        }
    }
    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;
}