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

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

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

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

    for (i = 1; i <= n; i++)    
        for (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";

    i = j = 1;
    while (i <= n && j <= m)
    {
        if (a[i] == b[j])
        {
            fout << a[i] << " ";
            i++;
            j++;
        }
        else if (dp[i + 1][j] >= dp[i][j + 1])
            i++;
        else 
            j++;
    }
    return 0;
}