#include <stdio.h>
 
#define max(a,b) ((a>b) ? a : b)
#define NMax 1025
 
int M, N, A[NMax], B[NMax], D[NMax][NMax], sir[NMax], bst;
 
int main()
{
	int i,j;
 
	freopen("cmlsc.in", "r", stdin);
	freopen("cmlsc.out", "w", stdout);
 
	scanf("%d %d", &M, &N);
	for (i=1; i<=M; i++)
		scanf("%d", &A[i]);
	for (i=1; i<=N; i++)
		scanf("%d", &B[i]);
 
	for (i=1; i<=M; i++)
	for (j=1; j<=N; j++)
	if (A[i]==B[j])
		D[i][j] = 1 + D[i-1][j-1];
	else
		D[i][j] = max(D[i-1][j],D[i][j-1]);
	
	bst = 0;
	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;
}