#include <fstream>
#include <iostream>
using namespace std;

const int MAX = 1024+1;

int main() {
	ifstream in("cmlsc.in");
	ofstream out("cmlsc.out");

	int m,n;
	int a[MAX], b[MAX];
	int sol[MAX],prev[MAX],current[MAX],aux[MAX];

	in >> m >> n;
	a[0]=0; b[0]=0;
	for(int i=1;i<=m;i++) in >> a[i];
	for(int j=1;j<=n;j++) in >> b[j];

	for(int j=0;j<=n;j++){
		sol[j]=0;
		prev[j]=0;
		current[j]=0;
	} 
	
	int s0,s1,c0,c1;
	for(int i=1;i<=m;i++){
		s0=0, c0=0;
		for(int j=1;j<=n;j++){
			s1=sol[j]; c1=current[j];
			if (a[i]==b[j]){
				sol[j]=s0+1;
				prev[j]=c0;
				current[j]=j;
			}else{
				if(sol[j-1]>sol[j]){
					sol[j]=sol[j-1];
					prev[j]=prev[j-1];
					current[j]=current[j-1];
				}
			}
			s0=s1; c0=c1;
			// cerr<<"("<<sol[j]<<" "<<prev[j]<<" "<<current[j]<<")";
		}
		// cerr<<endl;
	}

	out << sol[n] << "\n";

	int solIndex=sol[n]-1;
	aux[solIndex]=b[current[n]];
	int prevj = prev[n];
	while(prevj!=0){
		--solIndex;
		aux[solIndex]=b[prevj];
		prevj=prev[prevj];
	}


	for(int k=0;k<sol[n];k++){
		out << aux[k] <<" ";
	}
	out << "\n";

	in.close();
	out.close();
	return 0;
}