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