class State:
    def __init__(self, id):
        self.id = id
        self.outs = []
        self.visited = False

    def __repr__(self):
        return str(self.id)

def dead(begins, all):
    def search(state):
        if state.visited:
            return
        state.visited = True
        for s in state.outs:
            search(s)

    for s in begins:
        search(s)

    removable = []

    for s in all:
        if not s.visited:
            removable.append(s);
    return removable

if __name__ == "__main__":
    ss = []
    for i in range(6):
        ss.append(State(i))
    ss[0].outs = [ss[5]]
    ss[1].outs = [ss[3],ss[2]]
    ss[2].outs = [ss[1]]
    ss[3].outs = [ss[2],ss[4]]
    ss[4].outs = []
    ss[5].outs = []
    print dead([ss[1]], ss)
    for s in ss:
        s.visited = False
    print dead([ss[0]], ss)
    for s in ss:
        s.visited = False
    print dead([ss[0],ss[1]], ss)