#include <cstdio>
long i,j,n,m,a[1025],b[1025],v[1025][1025],d[1025];
int main ()
{
	freopen("cmlsc.in","r",stdin);
	freopen("cmlsc.out","w",stdout);
	scanf("%ld%ld",&n,&m);
	for (i=1;i<=n;i++)
		scanf("%ld",&a[i]);
	for (j=1;j<=m;j++)
		scanf("%ld",&b[j]);
	for (i=1;i<=n;i++)
		for (j=1;j<=m;j++)
		{
			if (a[i]==b[j])
				v[i][j]=v[i-1][j-1]+1;
			else
				v[i][j]=(v[i][j-1]<v[i-1][j]?v[i-1][j]:v[i][j-1]);
		}
	for (i=n,j=m;i>0;)
	{
		if (a[i]==b[j])
		{
			d[++d[0]]=a[i];
			i--;
			j--;
		}
		else if (v[i-1][j]<v[i][j-1])
			j--;
		else
			i--;
	}
	printf("%ld\n",d[0]);
	for (i=d[0];i>0;i--)
		printf("%ld ",d[i]);
	return 0;
}