#include<fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int a[1025][1025],b[1025],c[1025],sub[1025];
int n,m,i,j,x=0;
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]);
		}
	g<<a[n][m]<<"\n";
	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--;
	}
	for(i=x;i>=1;i--)
		g<<sub[i]<<" ";
	return 0;
}