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

vector<int> a;
vector<vector<int> > adj, adj2, scc, b;
vector<bool> vis;
vector<int> topOrd;
int cnt = 0;

void dfs(int v) {
    vis[v] = 1;
    for(int u : adj[v]) {
        if(!vis[u]) {
            dfs(u);
        }
    }

    topOrd.push_back(v);
}

void dfs2(int v) {
    vis[v] = 1;
    scc[cnt].push_back(v);

    for(int u : adj2[v]) {
        if(!vis[u]) {
            dfs2(u);
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    a.assign(n+1, 0);
    adj.resize(n+m+1);
    adj2.resize(n+m+1);
    b.resize(n+m+1);
    vis.assign(n+m+1, 0);
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        adj[i].push_back(n+a[i]);
        adj[n+a[i]].push_back(i);
        adj2[i].push_back(n+a[i]);
        adj2[n+a[i]].push_back(i);
    }

    for(int i = 1; i <= n; i++) {
        int x;
        cin >> x;
        for(int j = 1; j <= x; j++) {
            int y;
            cin >> y;
            adj[n+y].push_back(i);
            adj2[i].push_back(n+y);
        }
    }

    for(int i = 1; i <= n+m; i++) {
        if (!vis[i]) {
            dfs(i);
        }
    }

    reverse(topOrd.begin(), topOrd.end());

    /*for(int &x : topOrd) {
        cout << x << ' ';
    }*/

    //cout << endl;

    vis.assign(n+m+1, 0);

    for(int x : topOrd) {
        if (!vis[x]) {
            scc.push_back({});
            dfs2(x);
            cnt++;
        }
    }


    int mx = 0, ind;


    for(int i = 0; i < cnt; i++) {
        //cout << i << endl;
        for(int &x : scc[i]) {
            if (x <= n) {
                b[i].push_back(x);
                //cout << x << ' ' << b[i].size() << endl;
            }
        }

        if (mx < b[i].size()) {
            mx = b[i].size();
            ind = i;
        }
        //out << endl;
    }

    cout << mx << endl;
    for(int &x : b[ind]) {
        cout << x << ' ';
    }


}