#include<fstream>
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
int a[1055],b[1055],v[1055],k,c[1055][1055],n,m;
int main(){
	int i,j;
	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]) 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;
}