#include <bits/stdc++.h>
using namespace std;
int main()
{
    //ifstream f("szamok.txt");
    int n,m,kezd,veg;
    cin>>n>>m>>kezd>>veg;
    vector<vector<int>>a(n+m+1);
    for(int i=1; i<=n; i++){
        int x; cin>>x;
        for(int j=0; j<x; j++){
            int y; cin>>y;
            a[y].push_back(m+i);
            a[m+i].push_back(y);}}
    vector<int>tav(n+m+1,1e9);
    vector<int>ut(n+m+1);
    queue<int>q;
    q.push(kezd);
    tav[kezd]=0;
    while(!q.empty()){
        int x=q.front();
        for(int i:a[x]){
            if(tav[i]>tav[x]+1){
                tav[i]=tav[x]+1;
                q.push(i);
                ut[i]=x;}}
        q.pop();}
    vector<int>nyom;
    if(tav[veg]==1e9){
        cout<<-1;}
    else{
        int t=veg;
        while(t!=kezd){
            t=ut[t];
            if(t>m)nyom.push_back(t-m);}
        reverse(nyom.begin(), nyom.end());}
    cout<<nyom.size()<<endl;
    for(int i:nyom)cout<<i<<" ";
    return 0;
}