#include <fstream>
using namespace std;

ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int a[1025][1025], b[1025], c[1025], sub[1025];
int main()
{ 
	int n,m,i,j,x=0;
	fin >> n >> m;
	for( i = 1; i <= n; i++ )
		fin >> b[i];
	for(i=1;i<=m;i++)
		fin >> c[i];
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			{
				if(b[i]==c[j])
					a[i][j]=a[i-1][j-1]+1;
				else
					a[i][j]=max(a[i-1][j], a[i][j-1]);

			} 
		i = n;
		j = m;
		while(a[i][j])
		{
			while(a[i][j]==a[i-1][j])
				i--;
			while(a[i][j]==a[i][j-1])
				j--;
				{
					x++;
					sub[x]=b[i];
				}
				i--;
				j--;
		}
		fout << a[n][m]<<"\n";
		for( i = x; i >= 1; i-- )
			fout << sub[i] << " ";
		return 0;

}