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

int n, m;
vector<vector<int>>g, g2;
vector<bool>vis;
vector<int>top, comp;

void dfs(int v)
{
    vis[v] = 1;
    for(int u : g[v]) if(!vis[u]) dfs(u);
    top.push_back(v);
}

void dfs2(int v)
{
    if(v < n) comp.push_back(v+1);
    vis[v] = 1;
    for(int u : g2[v]) if(!vis[u]) dfs2(u);
}

signed main() {
    ios::sync_with_stdio(false);cin.tie(nullptr);
    cin >> n >> m;
    g.resize(n+m); g2.resize(n+m); vis.resize(n+m);
    for(int i = 0; i < n; i++)
    {
        int x; cin >> x; x--;
        g[i].push_back(x+n);
        g[x+n].push_back(i);
        g2[i].push_back(x+n);
        g2[x+n].push_back(i);
    }
    for(int i = 0; i < n; i++)
    {
        int k; cin >> k;
        while(k--)
        {
            int x; cin >> x; x--;
            g[i].push_back(x+n);
            g2[x+n].push_back(i);
        }
    }
    for(int i = 0; i < n+m; i++) if(!vis[i]) dfs(i);
    reverse(top.begin(), top.end());
    vis.assign(n+m, 0);
    vector<int>ans;
    for(int v : top)
    {
        if(vis[v]) continue;
        dfs2(v);
        if((int)comp.size() > (int)ans.size()) ans = comp;
        comp.clear();
    }
    cout << (int)ans.size() << '\n';
    for(int u : ans) cout << u << " ";
}