下列C++代码用循环链表解决约瑟夫问题，即假设n个人围成一圈，从第一个人开始数，每次数到第 $k$ 个的人就出圈，输出最后留下的那个人的编号。横线上应填写（ ）。

struct Node {
    int data;
    Node* next;
};

Node* createCircularList(int n) {
    Node* head = new Node{1, nullptr};
    Node* prev = head;
    for (int i = 2; i <= n; ++i) {
        Node* node = new Node{i, nullptr};
        prev->next = node;
        prev = node;
    }
    prev->next = head;
    return head;
}

int fingLastSurvival(int n, int k) {
    Node* head = createCircularList(n);
    Node* p = head;
    Node* prev = nullptr;

    while (p->next != p) {
        for (int count = 1; count < k; ++count) {
            prev = p;
            p = p->next;
        }
        _______________________
    }

    cout << "最后留下的人编号是: " << p->data << endl;
    delete p;

    return 0;
}