#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
 
int rs[1030],r,A[1030],B[1030],D[1030][1030],M,N,i,j;
int main(){
	fin >> N >> M;
	for(i = 1;i<=N;i++){
		fin >> A[i];
	}
	for(i = 1;i<=M;i++){
		fin >> B[i];
	}
	
	for(i = 1;i<=N;i++)
		for(j = 1;j<=M;j++){
			D[i][j] = max(D[i-1][j],D[i][j-1]);
			if(A[i] == B[j]) D[i][j] = min(D[i-1][j],D[i][j-1]) +1;
		}
	fout << D[N][M]<<'\n';
	
	i = N;
	j = M;
	while(r < D[N][M]){
		for( ;D[i-1][j]!=D[i][j-1];j--);
		if(D[i-1][j] < D[i][j]) rs[++r] = A[i];
		i--;
	}
	for(i = r;i>0;i--) fout << rs[i] <<' ';
	return 0;
}