#include <iostream>
#include <fstream>

using namespace std;

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

int n, m, a[1025], b[1025], sub[1025], k, dp[1025][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])
            {
                sub[k++] = a[i];
                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';
    for(int i = 0; i < k; i++)
        fout << sub[i] << ' ';

    return 0;
}