struct Snake{
    Ringlet* head;
    Snake(Ringlet* _head){
        head = _head;
    }

    void append(Ringlet* ringlet){
        Ringlet* cur = head;
        while(cur->next != NULL){
            cur = cur->next;
        }
        cur->next = ringlet;
        ringlet->previous = head;
    }

    void prepend(Ringlet* ringlet){
        head->previous = ringlet;
        ringlet->next = head;
        head = ringlet;
    }

    void insert(Ringlet* before, Ringlet* ringlet){
        Ringlet* after = before->next;
        before->next = ringlet;
        ringlet->previous = before;
        ringlet->next = after;
        after->previous = ringlet;
    }

    void remove(Ringlet* ringlet){
        Ringlet* previous = ringlet->previous;
        Ringlet* next = ringlet->next;
        previous->next = next;
        next->previous = previous;
    }
};