#include <fstream>
#include <vector>

using namespace std;

ifstream f("cmlsc.in");
ofstream g("cmlsc.out");

int n, m, a[1050], b[1050], dp[1050][1050];
vector <int> sol;

int main()
{
    f >> n >> m;
    for(int i=1; i<=n; i++) f >> a[i];
    for(int i=1; i<=m; i++) f >> b[i];

    for(int i=1; i<=n; i++)
        for(int j=1; j<=m; j++)
        {   if(a[i] == b[j]) dp[i][j] = 1 + dp[i-1][j-1];
            else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        }
    g << dp[n][m] << '\n';

    int i = n;
    int j = m;
    while(i >= 1 && j >= 1)
    {
        if(a[i] == b[j]) sol.push_back(a[i]);
        if(dp[i-1][j] > dp[i][j-1]) i--;
        else j--;
    }
    for(int i=sol.size()-1; i>=0; i--) g << sol[i] << ' ';
    g << '\n';
    return 0;
}