#define _CRT_SECURE_NO_DEPRECATE

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <cstring>
#include <ctime>

#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <string>
#include <sstream>


typedef long long int64;
typedef long long li;
typedef long double ld;

using namespace std;

#define forn(i, n) for(int i = 0; i < int(n); ++i)
#define fore(i, l, r) for(int i = int(l); i < int(r); ++i)
#define forb(i, n) for(int i = int(n) - 1; i >= 0; --i)

#define fr first
#define sc second
#define mp make_pair
#define pb push_back

const li INF = 1000000002;
double e = 0.0000001;
const double pi=3.1415926535897932384626433832795;

vector<int> ans;
vector<bool> v;
vector<vector<int> > a;
int n, k;

void gen(int x, int c){
	if (c > n){
		cout << -1;
		exit(0);
	}
	forn(i, a[x].size()){
		if (!v[a[x][i]]){
			gen(a[x][i], c + 1);
		}
	}
	v[x] = 1;
	ans.push_back(x);
}

int main(){
//	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);

	cin >> n >> k;
	a.resize(n);
	vector<int> b(k);
	forn(i, k){
		cin >> b[i];
		b[i]--;
	}
	forn(i, n){
		int c;
		cin >> c;
		forn(j, c){
			int d;
			cin >> d;
			d--;
			a[i].push_back(d);
		}
	}
	v.resize(n);
	forn(i, k){
		if (!v[b[i]]){
			gen(b[i], 0);
		}
	}

	cout << ans.size() << endl;
	forn(i, ans.size()){
		cout << ans[i] + 1 << ' ';
	}
	return 0;
}