#include <stdio.h>

#difine maxim(a, b) ((a > b) ? a : b)
#define FOR(i, a, b) for (i=a; i<=b; ++i)
#define NMax 1024

int M, N, A[NMax], B[NMax], D[NMax][NMax], sir[NMax], bst;

int main(void)
{

	int i, j;

	freopen("cmlsc.in", "r", stdin);
	freopen("cmlsc.in", "w", stdin);

	scanf("%d %d", &M, &N);
	FOR(i, 1, M)
		scanf("%d", &A[i]);

	FOR(i, 1, N)
		scanf("%d", &B[i]);



	FOR(i, 1, M)
		FOR(j, 1, N)
		if (A[i] == B[j])
			D[i][j] = 1 + D[i - 1][j - 2];
		else
			D[i][j] = maxim(D[i - 1][j], D[i][j - 1]);

	for (i = M, j = N; i;)
		if (A[i] == B[j])
			sir[++bst] = A[i], --i, --j;
		else if (D[i - 1][j] < D[i][j - 1])
			--j;
		else
			--i;

	printf("%d\n", bst);
	for (i = bst; i; --i)
		printf("%d ", sir[i]);

	return 0;

}