#include <iostream>
#include <stack>
#include <vector>

using namespace std;

int n, m;

struct Nyelv{
    vector<int> beszelok;
    vector<int> adj;
    vector<int> radj;
    bool bejart = false;
    int scc = 0;
};

Nyelv a[100001];
int karakter[100001];
stack<int> s;
int sccCount = 0;
int sccSize = 0;
int maxi = 0;
int biggestscc;

void dfs1(int x){
    a[x].bejart = 1;
    for (auto& it : a[x].adj){
        if (!a[it].bejart){
            dfs1(it);
        }
    }
    s.push(x);
}

void dfs2(int x){
    a[x].scc = sccCount;
    for (auto& it : a[x].radj){
        if (!a[it].scc){
            dfs2(it);
        }
    }
    sccSize += a[x].beszelok.size();
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n >> m;
    for (int i = 1; i <= n; i++){
        int x;
        cin >> x;
        a[x].beszelok.push_back(i);
        karakter[i] = x;
    }

    for (int i = 1; i <= n; i++){
        int k;
        cin >> k;
        for (int j = 0; j < k; j++){
            int x;
            cin >> x;
            a[karakter[i]].adj.push_back(x);
            a[x].radj.push_back(karakter[i]);
        }
    }

    for (int i = 1; i <= m; i++){
        if (!a[i].bejart){
            dfs1(i);
        }
    }
    while (!s.empty()){
        int x = s.top();
        s.pop();
        if (!a[x].scc){
            sccSize = 0;
            sccCount++;
            dfs2(x);
            if (sccSize > maxi){
                maxi = sccSize;
                biggestscc = sccCount;
            }
        }
    }
    cout << maxi << '\n';
    for (int i = 1; i <= m; i++){
        if (a[i].scc == biggestscc){
            for (auto& it : a[i].beszelok){
                cout << it << ' ';
            }
        }
    }
}