#include <iostream>
#include <cstdlib>

#define max(a,b) ((a)>(b)?(a):(b))
#define Nmax 1024
#define Mmax 1024

void read(int *n, int *m, int **array_a, int **array_b)
{
	// read n and m
	std::cin >> *n >> *m;

	*array_a = (int *)malloc (*n * sizeof(int));
	*array_b = (int *)malloc (*m * sizeof(int));
	for (int i = 0; i < *n; ++i) {
		std::cin >> (*array_a)[i];	
	}

	for (int i = 0; i < *m; ++i) {
		std::cin >> (*array_b)[i];
	}
}

void print_reverse (int d[Nmax][Nmax], int *a, int *b, int n, int m)
{
	if (n < 0 || m < 0) {
		return;
	}
	if (a[n] == b[m]) {
		print_reverse(d, a, b, (n - 1), (m - 1));
		std::cout << a[n] << " ";
		return;
	}

	if (d[n - 1][m] > d[n][m - 1]) {
		print_reverse(d, a, b, (n - 1), m);
		return;
	}
	print_reverse(d, a, b, n, (m-1));
	return;
}

int cmlsc (int *a, int *b, int n, int m)
{
	int to_ret;
	int D[Nmax][Mmax];
	
	for (int i = 0; i < n; ++i) {
		if (a[i] == b[0]) {
			D[i][0] = 1;
		}
		else {
			D[i][0] = 0;
		}
	}

	for (int j = 0; j < n; ++j) {
		if (a[0] == b[j]) {
			D[0][j] = 1;
		}
		else {
			D[0][j] = 0;
		}
	}


	for (int i = 0; i < n; ++ i) {
		for (int j = 0; j < m; ++j) {
			if (a[i] == b[j]) {
				D[i][j] = D[i-1][j-1] + 1;
			} else {
				D[i][j] = max(D[i][j-1], D[i-1][j]);
			}
		}
	}

	std::cout << D[n-1][m-1] << std::endl;
	print_reverse(D, a, b, n - 1, m - 1);
}

int main()
{
	int n, m;
	int *a, *b;

	read (&n, &m, &a, &b);
	cmlsc (a, b, n, m);

	return 0;
}