/* Problem URL: https://cses.fi/problemset/task/3403 */

#include <bits/stdc++.h>

using namespace std;

#define V vector

#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)

#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)

#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()

using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;

using ll = long long;

using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;

template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
    os << vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        os << ' ' << vec[i];
    }
    os << '\n';
    return os;
}

template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
    for (auto &i : vec) {
        is >> i;
    }
    return is;
}

template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
    for (auto &i : vec) {
        os << i[0];
        for (size_t j = 1; j < i.size(); j++) {
            os << ' ' << i[j];
        }
        os << '\n';
    }
    return os;
}

template<class v>
auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
    for (auto &i : vec) {
        for (auto &j : i) {
            is >> j;
        }
    }
    return is;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    vi a(n);
    vi b(m);
    cin >> a >> b;

    vvi dp(n + 1, vi(m + 1));

    nrep(i, 1, n + 1) {
        nrep(j, 1, m + 1) {
            if (a[i - 1] == b[j - 1]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
                continue;
            }

            dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
    }

    cout << dp[n][m] << '\n';
    // if (dp[n][m] == 0) {
    //     return 0;
    // }

    vi ans(dp[n][m]);
    int act = dp[n][m] - 1;

    int i = n;
    int j = m;

    while (i > 0 && j > 0) {
        if (a[i - 1] == b[j - 1]) {
            ans[act] = a[i - 1];
            i--;
            j--;
            act--;
            continue;
        }

        if (dp[i - 1][j] > dp[i][j - 1]) {
            i--;
            continue;
        }

        j--;
    }

    cout << ans;
}