照着蓝书写的

#include<bits/stdc++.h>
#include<time.h>
using namespace std;
const int maxn=1e5+5;
const int INF=0x7fffffff;
struct node{
	int lc,rc;
	int val,dat;
	int num,size;
}tree[maxn];
int n,cnt,rt;
int add(int val){	
	tree[++cnt].val=val;
	tree[cnt].dat=rand();
	tree[cnt].num=tree[cnt].size=1;
	return cnt;
}
void upDate(int p){
	tree[p].size=tree[tree[p].lc].size+tree[tree[p].rc].size+tree[p].num;
}
void build(){
	add(-INF);add(INF);
	rt=1;
	tree[1].rc=2;
	upDate(rt);
}
int rankfindbyval(int p,int val){
	if(p==0)
		return 0;
	if(val==tree[p].val) 
		return tree[tree[p].lc].size+1;
	if(val<tree[p].val) 
		return rankfindbyval(tree[p].lc,val);
	return rankfindbyval(tree[p].rc,val)+tree[tree[p].lc].size+tree[p].num;
}
int valfindbyrank(int p,int rank){
	if(p==0)
		return INF;
	if(tree[tree[p].lc].size>=rank) 
		return valfindbyrank(tree[p].lc,rank);
	if(tree[tree[p].lc].size+tree[p].num>=rank) 
		return tree[p].val;
	return valfindbyrank(tree[p].rc,rank-tree[tree[p].lc].size-tree[p].num);
}
void zig(int &p){
	int q=tree[p].lc;
	tree[p].lc=tree[q].rc,tree[q].rc=p,p=q;
	upDate(tree[p].rc);
	upDate(p);
}
void zag(int &p){
	int q=tree[p].rc;
	tree[p].rc=tree[q].lc,tree[q].lc=p,p=q;
	upDate(tree[p].lc);
	upDate(p);
}
void inst(int &p,int val){
	if(p==0){
		p=add(val);
		return;
	}
	if(val==tree[p].val){
		tree[p].num++;upDate(p);
		return;
	}
	if(val<tree[p].val){
		inst(tree[p].lc,val);
		if(tree[p].dat<tree[tree[p].lc].dat){
			zig(p);
		}
	}
	else{
		inst(tree[p].rc,val);
		if(tree[p].dat<tree[tree[p].rc].dat){
			zag(p);
		}
	}
	upDate(p);
	
}
int getpre(int val){
	int ans=1;
	int p=rt;
	while(p){
		if(val==tree[p].val){
			if(tree[p].lc>0){
				p=tree[p].lc;
				while(tree[p].rc>0)p=tree[p].rc;
				ans=p;
			}
			break;
		}
		if(tree[p].val<val && tree[p].val>tree[ans].val)ans=p;
		p=val<tree[p].val? tree[p].lc:tree[p].rc;
	}
	return tree[ans].val;
}
int getnxt(int val){
	int ans=2;
	int p=rt;
	while(p){
		if(val==tree[p].val){
			if(tree[p].rc>0){
				p=tree[p].rc;
				while(tree[p].lc>0)p=tree[p].lc;
				ans=p;
			}
			break;
		}
		if(tree[p].val>val&&tree[p].val<tree[ans].val)ans=p;
		p=val<tree[p].val? tree[p].lc:tree[p].rc;
	}
	return tree[ans].val;
}
void del(int &p,int val){
	if(p==0){
		return;
	}
	if(val==tree[p].val){
		if(tree[p].num>1){
			tree[p].num--;
			upDate(p);
			return;
		}
		if(tree[p].lc||tree[p].rc){
			if(tree[p].rc==0||tree[tree[p].lc].dat>tree[tree[p].rc].dat){
				zig(p);
				del(tree[p].rc,val);
			}
			else{
				zag(p);
				del(tree[p].lc,val);
			}
			upDate(p);
		}
		else{
			p=0;
		}
		return;
	}
	val<tree[p].val? del(tree[p].lc,val):del(tree[p].rc,val);
	upDate(p);
}
int main(){
	build();
	srand((unsigned int)time(NULL));
	cin>>n;	
	for(int i=1;i<=n;i++){
		int opt,x;
		cin>>opt>>x;
		switch(opt){
			case 1:inst(rt,x);break;
			case 2:del(rt,x);break;
			case 3:printf("%lld\n",rankfindbyval(rt,x)-1);break;
			case 4:printf("%lld\n",valfindbyrank(rt,x+1));break;
			case 5:printf("%lld\n",getpre(x));break;
			case 6:printf("%lld\n",getnxt(x));break;
		}
	}
	
	return 0;
}