insert就出问题了，build好像可以成功运行
缺少什么注释写在评论区里，我后面再加
我太菜了，debug不出来

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>

using namespace std;

const int N = 100010, INF = 1e8;

struct Node
{
    Node *l, *r;
    int cnt, size;
    int key, val;
}*root;
int n;

template<typename T> inline void read(T &x) //快读
{
    x = 0;
    T f = 1;
    char ch = getchar();
    while (!isdigit(ch))
    {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (isdigit(ch))
    {
        x = x * 10 + ch - '0';
        ch = getchar();
    }
}

Node* get_node(int key) //创造初始化节点
{
    Node *p = new Node;
    p->key = key;
    p->val = rand();
    p->cnt = p->size = 1;
    return p;
}

void pushup(Node *p)    //更新父节点信息
{
    p->size = p->l->size + p->r->size + p->cnt;
}

void zag(Node *p)   //left rotate
{
    Node *q = p->r;
    p->r = q->l, q->l = p, p = q;
    pushup(p->l), pushup(p);
}

void zig(Node *p)   //right rotate
{
    Node *q = p->l;
    p->l = q->r, q->r = p, p = q;
    pushup(p->r), pushup(p);
}

void build()    //建树并设置哨兵节点
{
    root = get_node(-INF);
    Node *q = get_node(INF);
    root->r = q;
    if (q->val > root->val)
        zag(root);
    pushup(root);
}

void insert(Node *p, int key)   //插入
{
    if (!p) p = get_node(key);  //到了叶子节点，创建一个新节点
    else if (p->key == key) p->cnt ++ ; //已经存在，计数器++
    else if (p->key > key) //比根节点小，插入左子树，同时维护堆的性质，右旋
    {
        insert(p->l, key);
        if (p->l->val > p->val)
            zig(p);
    }
    else    //否则插入右子树，并维护堆的性质
    {
        insert(p->r, key);
        if (p->r->val > p->val)
            zag(p);
    }
    pushup(p);  //因为新增节点，重新计算每个节点的属性
}

void remove(Node *p, int key)
{
    if (!p) return;
    else if (p->key == key)
    {
        if (p->cnt > 1) p->cnt -- ;
        else if (p->l || p->r)
        {
            if (!p->l || p->r->val > p->l->val)
            {
                zag(p);
                remove(p->l, key);
            }
            else
            {
                zig(p);
                remove(p->r, key);
            }
        }
        else p = nullptr;
    }
    else if (p->key > key) remove(p->l, key);
    else remove(p->r, key);
    
    pushup(p);
}

int get_rank_by_key(Node *p, int key)
{
    if (!p) return INF;
    else if (p->key < key) return p->l->size + p->cnt + get_rank_by_key(p->r, key);
    else if (p->key == key) return p->l->size + 1;
    else return get_rank_by_key(p->l, key);
}

int get_key_by_rank(Node *p, int rank)
{
    if (!p) return INF;
    else if (p->l->size >= rank) return get_key_by_rank(p->l, rank);
    else if (p->l->size + p->cnt >= rank) return p->key;
    else return p->l->size + p->cnt + get_key_by_rank(p->r, rank - p->l->size - p->cnt);
}

int get_prev(Node *p, int x)    //严格小于x的最大数
{
    if (!p) return -INF;
    else if (p->key >= x) return get_prev(p->l, x);
    else return max(p->key, get_prev(p->r, x));
}

int get_nex(Node *p, int x)    //严格大于x的最小数
{
    if (!p) return INF;
    else if (p->key <= x) return get_nex(p->r, x);
    else return min(p->key, get_nex(p->l, x));
}

int main()
{
    read(n);
    build();
    while (n -- )
    {
        int opt, x;
        read(opt), read(x);
        switch(opt)
        {
            case 1:
                insert(root, x);
                break;
            case 2:
                remove(root, x);
                break;
            case 3:
                printf("%d\n", get_rank_by_key(root, x) - 1);
                break;
            case 4:
                printf("%d\n", get_key_by_rank(root, x + 1));
                break;
            case 5:
                printf("%d\n", get_prev(root, x));
                break;
            case 6:
                printf("%d\n", get_nex(root, x));
                break;
        }
    }
    return 0;
}