#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int MAXN = 100'001;

int b[MAXN], scc[MAXN], timer = 1;
bool vis[MAXN], vis2[MAXN];
vector<pair<int, int>> g[MAXN], g2[MAXN];
vector<int> comp;
stack<int> st;

void dfs(int u) {
    vis[u] = 1;
    for (auto [v, tmp] : g[u]) {
        if (!vis[v]) dfs(v);
    }
    st.push(u);
}

void dfs2(int u, int cc) {
    vis2[u] = 1;
    scc[u] = cc;
    comp.emplace_back(u);
    for (auto [v, tmp] : g2[u]) {
        if (!vis2[v]) dfs2(v, cc);
    }
}

int main() {
    int n, m; cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> b[i];
    for (int i = 1; i <= n; i++) {
        int k; cin >> k;
        g[b[i]].emplace_back(b[i], i);
        g2[b[i]].emplace_back(b[i], i);
        for (int j = 0; j < k; j++) {
            int x; cin >> x;
            g[x].emplace_back(b[i], i);
            g2[b[i]].emplace_back(x, i);
        }
    }
    for (int i = 1; i <= m; i++) {
        if (!vis[i]) dfs(i);
    }
    vector<int> ans;
    while (!st.empty()) {
        int u = st.top();
        st.pop();
        if (vis2[u]) continue;
        comp.clear();
        dfs2(u, timer++);
        set<int> curr;
        for (int v : comp) {
            for (auto [x, idx] : g2[v]) {
                if (scc[x] == scc[v]) {
                    curr.insert(idx);
                }
            }
        }
        if (curr.size() > ans.size()) {
            ans.clear();
            for (int x : curr) ans.emplace_back(x);
        }
    }
    cout << ans.size() << "\n";
    for (int x : ans) cout << x << " ";
    cout << "\n";
    return 0;
}