#include <bits/stdc++.h>

using namespace std;



vector<vector<int>> graph;
vector<vector<int>> allomas;
int main()
{
    int m,n,s,e;
    cin>>m>>n>>s>>e;
    allomas.resize(n);
    int x,y,z;
    vector<vector<int>> adat(m);
    for(int i=0;i<m;i++)
        {
        cin>>x;
        for(int j=0;j<x;j++)
            {
            cin>>y;
            allomas[y].push_back(i);
            adat[i].push_back(y);
            }
        }
/*
    for(auto x : adat)
        {
        for(int i=0;i<x.size();i++)
            {
            cout<<x[i]<<" ";
            }
        cout<<endl;
        }
*/
    vector<vector<int>> ans(m+1);
    if(allomas[e].size()==0)
        {
        cout<<-1;
        return 0;
        }
    queue<int> q;
    vector<bool> visitedallomas(m,false);
    for(auto x : allomas[s])
        {
        visitedallomas[x]=true;
        ans[x].push_back(x);
        q.push(x);
        }
    while(!q.empty())
        {
        int most=q.top();q.pop();
        for(auto x : adat[most])
            {
            for(auto y : allomas[x])
                {
                if(y==e)
                    {

                    }
                if(!visitedallomas[y])
                    {
                    visitedallomas[y]=true;
                    ans[y]=ans[x];
                    ans[y]
                    q.push(y);
                    }
                }
            }
        }
    return 0;
}