#include <cstdlib>
#include <fstream>

using namespace std;

const int NMAX = 1031;

int v[3][NMAX];
int dp[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 = 0; i < 2; ++i)
	{
		for(j = 1; j <= v[i][0]; ++j) 
		{
			in >> v[i][j];
		}
	}
	for(i = 1; i <= v[0][0]; ++i)
	{
		for(j = 1; j <= v[1][0]; ++j)
		{
			if(v[0][i] == v[1][j]) dp[i][j] = 1 + dp[i - 1][j - 1];
			else dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
		}
	}
	k = v[2][0] = dp[i = v[0][0]][j = v[1][0]];
	while(i && j)
	{
		if(v[0][i] == v[1][j])
		{
			v[2][k--] = v[0][i--];
			--j;
		}
		else if(dp[i - 1][j] >= dp[i][j - 1]) --i;
		else --j;
	}
	out << v[2][0] << '\n';
	for(i = 1; i <= v[2][0]; ++i)
	{
		out << v[2][i] << ' ';
	}
	out << '\n';
	
	return EXIT_SUCCESS;
}