#include <bits/stdc++.h>

using namespace std;

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

int m, n, x, cmlsc[1027][1027], t[1027];
vector<int> a, b;

int main()
{
    f >> m >> n;
    
    // index from 1
    a.push_back(0);
    b.push_back(0);

    while (m--) f >> x, a.push_back(x);
    while (n--) f >> x, b.push_back(x);

    for (int i = 1; i < a.size(); ++i)
        for (int j = 1; j < b.size(); ++j)
            if (a[i] == b[j])
                cmlsc[i][j] += cmlsc[i - 1][j - 1] + 1;
            else
                cmlsc[i][j] = max(cmlsc[i - 1][j], cmlsc[i][j - 1]);

    g << cmlsc[a.size() - 1][b.size() - 1] << '\n';
    
    vector<int> sol;

    for (int i = a.size() - 1, j = b.size() - 1; i > 0 && j > 0;)
        if (a[i] == b[j])
            sol.push_back(a[i]), --i, --j;
        else
            if (cmlsc[i - 1][j] < cmlsc[i][j - 1])
                --j;
            else
                --i;

    for (int i = sol.size() - 1; i >= 0; --i)
        g << sol[i] << ' ';

    return 0;
}