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]

    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:
            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()