#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]<<endl;
		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;
}