#include<cstdio>

int lung[1025][1025];
int a[1025];
int b[1025];

int n,m;

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

int max(int x,int y){
	if(x>y) return x;
	return y;
}

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

int cmbk(int i,int j){
	
	while(i>0 && j>0){
		if(a[i]==b[j]){
			cmbk(i-1,j-1);
			printf("%d ",a[i]);
			return 0;
		}
		else if(i-1>0 && lung[i][j]==lung[i-1][j])
			i--;
		else j--;
	}
	
}

int main(){
	
	freopen("cmlsc.in","r",stdin);
	freopen("cmlsc.out","w",stdout);
	
	read();
	
	printf("%d\n",lngh());
	
	cmbk(n,m);
	
	return 0;
	
}