#include <iostream>
#include <algorithm> // for sort, mainly
#include <vector>
#include <map>
#include <set>
#include <cmath>
#include <array>
#include <string>
#include <cstdio>
#include <iterator>
#include <unordered_set>
#include <cstdint> // for int64_t, int32_t, etc
#include <queue>
#include <stack>
#include <deque>
#include <numeric> // gcd, lcm
#include <fstream>
#include <bitset> // for bitset
#include <iomanip>
#include <cassert> // for set with custom ordering
#include <type_traits> // for set with custom ordering
#include <utility> // for swap, forward, etc
using namespace std;

#pragma GCC optimize("O2")
// #pragma GCC optimize("O1","O2","O3","Ofast","unroll-loops")
// #pragma GCC target("sse","sse2","sse3","sse4.1","sse4.2","avx","avx2","fma")

template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
void dbg_out() { cout << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cout << ' ' << H; dbg_out(T...); }
#ifdef LOCAL
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

/*

notes:

int64_t
stoi(string s) -> string to int
to_string() -> int (or else) to string

vector declaration:
vector<ll> v(n, 0)
vector<vector<ll>> v(n, vector<ll>(n, 0));

{if statement} ? {truth value} : {false value}

#ifdef LOCAL
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
#endif

std::lcm(ll a, ll b), std::gcd(int a, int b)

cout << fixed << setprecision(n);

set with custom ordering
set<ll, decltype(&cmp)> qu(cmp);

*/

typedef int64_t ll;

void vcerr(vector<vector<pair<ll,ll>>> v, ll n) {

	for(ll i = 1; i <= n; i++) {
		cerr << "\n" << i << " : ";
		cerr << v[i]; 
	}

}

void solve() {

	ll n, m, qs, qe; // query start query end
	cin >> n >> m >> qs >> qe;

	const ll inf = INT64_MAX / 2;

	vector<vector<pair<ll,ll>>> v(m+1);
	vector<ll> d(m+1, inf);

	for(ll i = 1; i <= n; i++) {

		ll k = 0;
		cin >> k;

		vector<ll> h(k, 0);
		for(ll j = 0; j < k; j++) {
			cin >> h[j];
		}

		//cerr << "\ni=" << i << "; h=" << h;

		for(ll a = 0; a < k; a++) {
			for(ll b = a + 1; b < k; b++) {

				v[h[a]].push_back({h[b], i});
				v[h[b]].push_back({h[a], i});

			}
		}

		//vcerr(v, m);

	}

	vector<ll> p(m+1, 0);
	queue<ll> q;
	q.push(qs);
	d[qs] = 0;
	while(!q.empty()) {

		ll curr = q.front();
		q.pop();

		for(const auto & [neigh, rail] : v[curr]) {
			if(d[neigh] == inf) {
				d[neigh] = d[curr] + 1;
				p[neigh] = curr;
				q.push(neigh);
			}
		}
	}

	//cerr << "\nd=" << d;
	//cerr << "\np=" << p;

	if(d[qe] == inf) {
		cout << "-1";
		return;
	}

	vector<ll> path;
	ll curr = qe;
	while(curr != qs) {

		//cerr << "\ncurr=" << curr;

		ll here = curr;
		ll before = p[curr];

		for(const auto & [neigh, rail] : v[before]) {
			if(neigh == curr) {
				path.push_back(rail);
			}
		}

		curr = p[curr];

	}

	reverse(path.begin(), path.end());
	cout << path.size() << "\n";
	for(const auto & x : path) {
		cout << x << " ";
	}


}

int main()
{
	std::ios_base::sync_with_stdio(false);
	//cin.tie(nullptr);
	//cout.tie(nullptr);

	solve();

	return 0;
}