#include<fstream>
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
int a[1025],b[1025],c[1025][1025],m,n,v[1025],k;
int main(){
	int i,j;
	in>>n>>m;
	for(i=1;i<=n;i++)
		in>>a[i];
	for(j=1;j<=m;j++)
		in>>b[j];
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++){
			if(a[i]==b[j])
				c[i][j]=c[i-1][j-1]+1;
			else{
				if(c[i-1][j]>=c[i][j-1])
					c[i][j]=c[i-1][j];
				else
					c[i][j]=c[i][j-1];
			}
		}
		out<<c[n][m]<<'\n';
	i=n;
	j=m;
	k=c[n][m];
	while(i && j){
		if(a[i]==b[j]){
			v[k--]=a[i];
			i--;
			j--;
		}
		else
			if(c[i-1][j]>=c[i][j-1])
				i--;
			else j--;
	}
	k=c[n][m];
	for(i=1;i<=k;i++)
		out<<v[i]<<" ";
	return 0;
}