#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 1024

using namespace std;

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

int n, m, a[NMAX+10], b[NMAX+10], dp[NMAX+10][NMAX+10], ans;
vector <int> sol;
pair <int, int> poz;

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];
                dp[i][j] = max(dp[i][j], dp[i-1][j]);
                dp[i][j] = max(dp[i][j], dp[i][j-1]);
                ans = max(ans, dp[i][j]);
            }
    g << ans << '\n';
    int i = n, j = m;
    while(i && j)
        {   if(a[i] == b[j])
                {   sol.push_back(a[i]);
                    i--;
                    j--;
                }
            else 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;
}