#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m, ind, erk;
    cin >> n >> m >> ind >> erk;
    vector<vector<int>> adj(n + m + 1);
    for (int i = 1; i <= n; i++)
    {
        int x; cin >> x;
        for (int y = 0; y < x; y++)
        {
            int z; cin >> z;
            adj[z].push_back(m + i);
            adj[m + i].push_back(z);
        }
    }
    vector<bool> visited(n+m + 1, false);
    vector<int> honnan(n+m + 1, -1);
    queue<int> q;
    q.push(ind);
    visited[ind] = true;
    while (!q.empty())
    {
        int v = q.front();
        if (v == erk)
            break;
        q.pop();
        for (int i = 0; i < adj[v].size(); i++)
        {
            if (!visited[adj[v][i]])
            {
                honnan[adj[v][i]] = v;
                visited[adj[v][i]] = true;
                q.push(adj[v][i]);
            }
        }
    }
    if (!visited[erk])
        cout << -1;
    else
    {
        vector<int> res;
        int i = erk;
        while (honnan[i] != ind)
        {
            if(honnan[i]>m)
                res.push_back(honnan[i]);
            i = honnan[i];
        }
        cout << res.size() << endl;
        reverse(res.begin(), res.end());
        for (auto x : res)
            cout << x-m << " ";
    }
}