#include <bits/stdc++.h>
using namespace std;

ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int n,m;
int dp[1025][1025];
int a[1025],b[1025],sir[1025];
int main()
{
    fin >> n >> m;
    for (int i = 1; i <= n; i++)
        fin >> a[i];
    for (int j = 1; j <= m; j++)
        fin >> b[j];
    for(int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
        {
            if (a[i] == b[j])
                dp[i][j] = dp[i - 1][j - 1] + 1;
            else dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
    fout << dp[n][m] << "\n";
    int i, j,p = 0;
    i = n; j = m;
    while (i > 0 && j > 0)
    {
        if (a[i] == b[j])
        {
            sir[++p] = a[i];
            i--;
            j--;
        }
        else if (dp[i - 1][j] < dp[i][j - 1])
            j--;
        else i--;
    }
    for (int i = p; i >= 1; i--)
        fout << sir[i] << " ";
    fin.close();
    fout.close();
    return 0;
}