// Galatan Tudor - Ion Luca High School
// Husi, Romania, Su, August 30, 2015

#include <fstream>

using namespace std;

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

int mx[1024][1024];
int a[1024], b[1024], sub[1024];
int n, m, i, j, x=0;

int main ()
{
	in >> n >> m;
	for (i=1; i<=n; i++)
		in >> a[i];
	for (i=1; i<=m; i++)
		in >> b[i];
	for (i=1; i<=n; i++)
		for (j=1; j<=m; j++)
		{
			if (a[i] == b[j])
				mx[i][j] = mx[i-1][j-1]+1;
			else
				mx[i][j] = max (mx[i-1][j], mx[i][j-1]);
		}
	i = n;
	j = m;
	while (mx[i][j])
	{
		while (mx[i][j] == mx[i-1][j])
			i--;
		while (mx[i][j] == mx[i][j-1])
			j--;
		x++;
		sub[x] = b[i];
		i--, j--;
	}
	out << mx[n][m] << "\n";
	for (i=x; i>=1; i--)
		out << sub[x] << " ";
	return 0;
}