def main3():
    N, M, Dep, Arr = map(int, input().split())
    metro = []
    Dep_index = set()
    Arr_index = set()
    for i in range(N):
        asd = list(map(int, input().split()))

        metro.append(set(asd[1:]))
        if Dep in metro[i]:
            Dep_index.add(i)
        if Arr in metro[i]:
            Arr_index.add(i)
        if i in Arr_index and i in Dep_index:
            print(1)
            print(i+1)
            return

    graph={}

    for i in range(N-1):
        for j in range(i+1, N):
            if not metro[i].isdisjoint(metro[j]):
                try:
                    graph[i].append(j)
                except:
                    graph[i] = [j]
                try:
                    graph[j].append(i)
                except:
                    graph[j] = [i]

    touched = Dep_index.copy()
    current_res = [0]*N
    for i in Dep_index:
        current_res[i]=[i]
    while Dep_index:
        tmp=[]
        for i in Dep_index:
            if i not in graph:
                continue
            for j in graph[i]:
                if j not in touched:
                    tmp.append(j)
                    touched.add(j)
                    current_res[j]=current_res[i]+[j]
                    if j in Arr_index:
                        print(len(current_res[j]))
                        [print(x+1, end=" ") for x in current_res[j]]
                        return
        Dep_index=tmp

    print("-1")

main3()