#include <fstream>
#include <vector>
#include <iterator>
using namespace std;

vector<short> kozos;

short max(short a, short b) {
	if (a > b) return a;
	return b;
}

void cmls(short A[], short **tomb, short i, short j) {
	if (i == 0 || j == 0) return;
	if (tomb[i][j] == tomb[i - 1][j]) {
		cmls(A, tomb, i - 1, j);
		return;
	}
	if (tomb[i][j] == tomb[i][j - 1]) {
		cmls(A, tomb, i, j - 1);
		return;
	}
	kozos.push_back(A[i]);
	cmls(A, tomb, i - 1, j - 1);
}

int main() {
	ifstream in("cmlsc.in");
	ofstream out("cmlsc.out");
	short N, M;
	in >> N >> M;

	short* A = new short[N+1];
	short* B = new short[M+1];

	for (int i = 1;i <= N;++i) in >> A[i];
	for (int i = 1;i <= M;++i) in >> B[i];

	short** tomb = new short*[N+1];
	for (int i = 0;i <= N;++i)
		tomb[i] = new short[M+1];
	
	for (int i = 0;i <= N;++i) tomb[i][0] = 0;
	for (int i = 1;i <= M;++i) tomb[0][i] = 0;

	for (int i = 1;i <= N;++i) 
		for (int j = 1;j <= M;++j) 
			if (A[i] == B[j]) tomb[i][j] = tomb[i - 1][j - 1] + 1;
			else tomb[i][j] = max(tomb[i - 1][j], tomb[i][j - 1]);

	out << tomb[N][M] << "\n";

	cmls(A,tomb,N,M);

	while (!kozos.empty()) {
		out << kozos.back()<<" ";
		kozos.pop_back();
	}
}