#include <vector>
#include <cstdlib>
#include <fstream>

using namespace std;
const int NMAX = 1031;
typedef vector<int> array;

int v[3][NMAX];
int C[NMAX][NMAX];

inline int _max(int x, int y) {return x >= y ? x : y;}
int main()
{
	int i, j, k;
	ifstream in("cmlsc.in");
	ofstream out("cmlsc.out");
	
	in >> v[0][0] >> v[1][0];
	
	for(i = 1; i <= v[0][0]; ++i)
	{
		in >> v[0][i];
	}
	for(j = 1; j <= v[1][0]; ++j)
	{
		in >> v[1][j];
	}
	
	for(i = 1; i <= v[0][0]; ++i)
	{
		for(j = 1; j <= v[1][0]; ++j)
		{
			if(v[0][i] == v[1][j]) C[i][j] = 1 + C[i-1][j-1];
			else C[i][j] = _max(C[i-1][j], C[i][j-1]);
		}
	}
	
	v[2][0] = C[v[0][0]][v[1][0]];
	for(i = v[0][0], j = v[1][0], k = v[2][0]; k; )
	{
		if(v[0][i] == v[1][j]) v[2][k--] = v[1][j], --i, --j;
		else if(C[i-1][j] >= C[i][j-1]) --i;
			 else --j;
	}
	
	out << v[2][0] << '\n';
	for(i = 1; i <= v[2][0]; ++i) out << v[2][i] << ' ';
	
	return EXIT_SUCCESS;
}