#include <stdio.h>
int max[1030][1030];
int a[1030],b[1030];
int m,n;

int maximum(int a,int b){return a>b?a:b;}

void back(int i,int j){
	if(!(i>0 && j>0)) return;
	if(a[i]==b[j]){  back(i-1,j-1);printf("%d ",a[i]);}
	else
	{	if(max[i][j-1]>=max[i-1][j])
			back(i,j-1);
		else
		back(i-1,j);
	}

}

int main(){

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

	scanf("%d",&n);scanf("%d",&m);
	for(int i=1;i<=n;i++)scanf("%d",&a[i]);
	for(int i=1;i<=m;i++)scanf("%d",&b[i]);

	for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
		{
			if(a[i]==b[j])
			max[i][j]=max[i-1][j-1]+1;
			else
				max[i][j]=maximum(max[i-1][j],max[i][j-1]);
		}
	printf("%d\n",max[n][m]-1);
	back(n,m);
	return 0;
}