#include <bits/stdc++.h>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int n, m, 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 = n; j = m;
    while (i > 0 && j > 0)
    {
        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;
}