#include <iostream>
#include <vector>
#include <climits>
using namespace std;

int n, m, beg, arr, best = INT_MAX;
vector<vector<pair<int, int>>> edges;
vector<int> sol;

void solve(vector<bool> vis, vector<int> s, int node) {
	vis[node] = true;
	if (node == arr - 1) {
		if (s.size() < best) {
			best = s.size();
			sol = s;
		}
		return;
	}
	for (pair<int, int> p : edges[node]) {
		int x = p.second, r = p.first;
		if (vis[x]) continue;
		bool added = false;
		if (s.empty()) {
			added = true;
			s.push_back(r);
		}
		if (s.back() != r) {
			added = true;
			s.push_back(r);
		}
		solve(vis, s, x);
		if (added) s.pop_back();
	}
	return;
}

int main() {
	cin >> n >> m >> beg >> arr;
	edges.resize(m);
	for (int i = 0; i < n; i++) {
		int k, prev;
		cin >> k >> prev;
		for (int j = 1; j < k; j++) {
			int x;
			cin >> x;
			edges[x - 1].push_back({ i + 1, prev - 1 });
			edges[prev - 1].push_back({ i + 1, x - 1 });
			prev = x;
		}
	}
	solve(vector<bool>(m, false), vector<int>(0), beg - 1);
	cout << sol.size() << "\n";
	for (int x : sol) cout << x << " ";
	return 0;
}