#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
int n, m, source, dest, ptr;
vector <VI> a;
VI d, d2, fifo, fifo2;
VPII p, p2;
VVI corresponding;
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);
d2.RS(m + 1, -1);
p.RS(m + 1);
p2.RS(m + 1);
fifo.RS(m + 1);
fifo2.RS(m + 1);
int l = 1, r = 1, l2 = 1, r2 = 1;
fifo[1] = source;
fifo2[1] = dest;
d[source] = 0;
d2[dest] = 0;
int meet = -1;
while (l <= r || l2 <= r2)
{
if (l <= r)
{
int node = fifo[l];
++l;
for (int i : corresponding[node])
{
for (int next : a[i])
if (d[next] == -1)
{
d[next] = d[node] + 1;
p[next] = {node, i};
if (d2[next] != -1)
{
meet = next;
break;
}
fifo[++r] = next;
}
if (meet != -1) break;
}
if (meet != -1) break;
}
if (l2 <= r2)
{
int node = fifo2[l2];
++l2;
for (int i : corresponding[node])
{
for (int next : a[i])
if (d2[next] == -1)
{
d2[next] = d2[node] + 1;
p2[next] = {node, i};
if (d[next] != -1)
{
meet = next;
break;
}
fifo2[++r2] = next;
}
if (meet != -1) break;
}
if (meet != -1) break;
}
}
if (meet != -1)
{
cout << d[meet] + d2[meet] << endl;
int node = meet;
VI sol;
while (node != source)
{
sol.PB(p[node].Y);
node = p[node].X;
}
reverse(ALL(sol));
node = meet;
while (node != dest)
{
sol.PB(p2[node].Y);
node = p2[node].X;
}
for (int x : sol) cout << x << " ";
}
else cout << -1;
return 0;
}