#include<fstream>
#define DIM 1025
using namespace std;

void Write(int, int);

ifstream fin ("cmlsc.in");
ofstream fout ("cmlsc.out");
int a[DIM], b[DIM], c[DIM][DIM];
int n, m;

int main()
{
	int i, j;
	fin >> n >> m;
	for ( i = 1; i <= n; ++i)
		fin >> a[i];
	for ( j = 1; j <= m; ++j )
		fin >> b[j];
	
	for ( i = 1; i <= n; ++i )
		for ( j = 1; j <= m; ++j )
			if ( a[i] == b[j] )
				c[i][j] = c[i-1][j-1] + 1;
			else
				c[i][j] = max( c[i-1][j], c[i][j-1] );
			
	fout << c[n][m] << '\n';
	Write(n, m );
	fin.close();
	fout.close();
}

void Write( int i, int j)
{
	if ( i == 0 || j == 0 )
		return;
	if ( a[i] == b[j] )
	{
		Write( i-1, j-1 );
		fout << a[i] << ' ';
	}
	else
		if ( c[i-1][j] > c[i][j-1] )
			Write( i - 1, j );
		else
			Write( i, j - 1);
}