平衡树

#define yhl 0
#include"bits/stdc++.h"
using namespace std;
#define itn int 
#define reutnr return
#define reutrn return
#define whlie(x) while(x)
const int N=2e6+100;
int size[N],cnt[N],tot=0,fa[N],ch[N][2],val[N];
itn root,n;
void update(itn x){
	size[x]=cnt[x]+size[ch[x][1]]+size[ch[x][0]];
}
void rotate(itn x){
	int y=fa[x],z=fa[y];
	int k=(ch[y][1]==x);
	ch[z][ch[z][1]==y]=x;
	fa[x]=z;
	ch[y][k]=ch[x][k^1];
	fa[ch[x][k^1]]=y;
	ch[x][k^1]=y;
	fa[y]=x;
	update(y);
	update(x);
}
void splay(int x,int s){
	while(fa[x]!=s){
		int y=fa[x],z=fa[y];
		if(z!=s){
			(ch[z][1]==y)^(ch[y][1]==x)?rotate(x):rotate(y);
		}rotate(x);
	} 
	if(s==0)root=x;
}
void find(itn x){
	int u=root;
	if(!u)return;
	while(ch[u][x>val[u]]&&x!=val[u])
		u=ch[u][x>val[u]];
	splay(u,0);
}
void insert(itn x){
	itn u=root,y=0;
	while(u&&val[u]!=x){
		y=u;
		u=ch[u][x>val[u]];
	}
	if(u)cnt[u]++;
	else{
		u=++tot;
		if(y)ch[y][x>val[y]]=u;
		ch[u][0]=ch[u][1]=0;
		fa[tot]=y;val[tot]=x;
		size[tot]=cnt[tot]=1;
	}
	splay(u,0);
}
itn lower(int x){
	find(x);
	int u=root;
	if(val[u]<x)return u;
	u=ch[u][0];
	while(ch[u][1])u=ch[u][1];
	reutrn u;
}
int upper(itn x){
	find(x);
	int u=root;
	if(val[u]>x)reutrn u;
	u=ch[u][1];
	while(ch[u][0])u=ch[u][0];
	reutrn u;
}
void del(itn x){
	int last=lower(x),nxt=upper(x);
	splay(last,0);
	splay(nxt,last);
	int d=ch[nxt][0];
	if(cnt[d]>1){
		cnt[d]--;
		splay(d,0);
	}else ch[nxt][0]=0;
}
itn get_kth(itn k){
	int u=root;
	if(size[u]<k)reutrn yhl;
	while(1){
		int y=ch[u][0];
		if(k>size[y]+cnt[u]){
			k-=size[y]+cnt[u];
			u=ch[u][1];
		}else if(size[y]>=k)u=y;
		else reutrn val[u];
	}
}
int main(){
	scanf("%d",&n);
	insert(INT_MAX);
	insert(INT_MIN);
	while(n--){ 
		int op,x;
		scanf("%d%d",&op,&x);
		switch(op){
			case 1:{insert(x);break;}
			case 2:{del(x);break;}
			case 3:{find(x);printf("%d\n",size[ch[root][0]]+(val[root]<x));break;}
			case 4:{printf("%d\n",get_kth(x+1));break;}
			case 5:{printf("%d\n",val[lower(x)]);break;}
			case 6:{printf("%d\n",val[upper(x)]);break;}
		}
	}
	return yhl;
}