#include <vector>
#include <string>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <bitset>
#include <stack>
#include <list>
#include <numeric>
#include <algorithm>
#include <random>
#include <chrono>
#include <cstdio>
#include <fstream>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <climits>
#include <cctype>
#include <cmath>
#include <ctime>
#include <cassert>
using namespace std;
#define ULL unsigned long long
#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VLL vector <LL>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >
#define SI set < int >
#define USI unordered_set <int>
#define MII map <int, int>
#define UMII unordered_map <int, int>
#define MS multiset
#define US unordered_set
#define UM unordered_map
#define UMS unordered_multiset
#define UMM unordered_multimap
#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define SZ size()
#define BG begin()
#define EN end()
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()
#define INS insert
#define ER erase
#define CNT count
#define IN_FILE "a.in"
#define OUT_FILE "a.out"
int n, m, source, dest, ptr;
vector <VI> a;
VI d, fifo;
VPII p;
VVI corresponding;
VB used;
string s;
int getInt()
{
int ans = 0;
while (!isdigit(s[ptr])) ++ptr;
while (isdigit(s[ptr])) ans = ans * 10 + (s[ptr++] - '0');
return ans;
}
int main()
{
ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
cin >> n >> m >> source >> dest;
corresponding.RS(m + 1);
a.RS(n + 1);
getline(cin, s);
FOR(i, 1, n)
{
getline(cin, s);
ptr = 0;
int c = getInt();
FOR(j, 1, c)
{
int x = getInt();
a[i].PB(x);
corresponding[x].PB(i);
}
}
d.RS(m + 1, -1);
p.RS(m + 1);
fifo.RS(m + 1);
used.RS(n + 1);
int l = 1, r = 1;
fifo[1] = source;
d[source] = 0;
while (l <= r)
{
int node = fifo[l];
++l;
for (int i : corresponding[node])
{
if (used[i]) continue;
used[i] = true;
for (int next : a[i])
if (d[next] == -1)
{
d[next] = d[node] + 1;
p[next] = {node, i};
if (next == dest) break;
fifo[++r] = next;
}
if (d[dest] != -1) break;
}
if (d[dest] != -1) break;
}
if (d[dest] != -1)
{
cout << d[dest] << endl;
int node = dest;
VI sol;
while (node != source)
{
sol.PB(p[node].Y);
node = p[node].X;
}
reverse(ALL(sol));
for (int x : sol) cout << x << " ";
}
else cout << -1;
return 0;
}