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

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

int m, n;
int a[1030], b[1030];
int dp[1030][1030];

vector <int> v;
int main()
{
    in >> m >> n;

    for (int i = 1; i <= m; i++)
    {
        in >> a[i];
    }

    for (int i = 1; i <= n; i++)
    {
        in >> b[i];
    }


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

    out << dp[m][n] << "\n";
    for (auto& x : v)
    {
        out << x << " ";
    }
    return 0;
}