#include <iostream>
using namespace std;
typedef long long ll;
ll opt,asks,num,pos=0,ovrmin=0x7fffffff,ovrmax=-10000001;
ll nums[100001];
struct Node{
	ll num,height,size,count;
	Node *Left,*Right;
	Node(ll x,ll y,ll z):num(x),height(y),size(z),count(1),Left(NULL),Right(NULL){}
}*Root;
ll getBalance(Node* x){return (x->Left==NULL?0:x->Left->height)-(x->Right==NULL?0:x->Right->height);}
Node* RR(Node* x){
	Node* y=x->Left;
	x->Left=(y->Right==NULL?NULL:y->Right);
	y->Right=x;
	x->height=max((x->Left==NULL?0:x->Left->height),(x->Right==NULL?0:x->Right->height))+1;
	x->size=(x->Left==NULL?0:x->Left->size)+(x->Right==NULL?0:x->Right->size)+x->count;
	y->height=max((y->Left==NULL?0:y->Left->height),(y->Right==NULL?0:y->Right->height))+1;
	y->size=(y->Left==NULL?0:y->Left->size)+(y->Right==NULL?0:y->Right->size)+y->count;
	return y;
}
Node* LL(Node* x){
	Node* y=x->Right;
	x->Right=(y->Left==NULL?NULL:y->Left);
	y->Left=x;
	x->height=max((x->Left==NULL?0:x->Left->height),(x->Right==NULL?0:x->Right->height))+1;
	x->size=(x->Left==NULL?0:x->Left->size)+(x->Right==NULL?0:x->Right->size)+x->count;
	y->height=max((y->Left==NULL?0:y->Left->height),(y->Right==NULL?0:y->Right->height))+1;
	y->size=(y->Left==NULL?0:y->Left->size)+(y->Right==NULL?0:y->Right->size)+y->count;
	return y;
}
Node* Avalon(Node* x){
	ll fh=getBalance(x),lh=0,rh=0;
	if(x->Left!=NULL) lh=getBalance(x->Left);
	if(x->Right!=NULL) rh=getBalance(x->Right);
	if(fh>=-1&&fh<=1) return x;
	if(fh>1){
		if(lh>0) x=RR(x);
		else if(lh<0){x->Left=LL(x->Left);x=RR(x);}
	}
	else if(fh<-1){
		if(rh>0){x->Right=RR(x->Right);x=LL(x);}
		else if(rh<0) x=LL(x);
	}
	return x;
}
Node* add(ll x,Node* y){
	ovrmin=min(ovrmin,x);
	ovrmax=max(ovrmax,x);
	if(y==NULL) return new Node(x,1,1);	
	if(y->num==x){
		y->count++;
		return y;
	}
	if(x<y->num){
		if(y->Left==NULL) y->Left=new Node(x,1,1);
		else y->Left=add(x,y->Left);
	}
	else{
		if(y->Right==NULL) y->Right=new Node(x,1,1);
		else y->Right=add(x,y->Right);
	}
	y->size++;
	y->height++;
	return Avalon(y);
}
Node* remove(ll x,Node* y){
	if(y->num==x){
		if(y->Left==NULL&&y->Right==NULL){
			y->count--;
			y->size--;
			if(y->count) return y;
			return NULL;
		}
		else if(!(y->Left!=NULL&&y->Right!=NULL)){
			y->count--;
			y->size--;
			if(y->count) return y;
			return y->Left==NULL?y->Right:y->Left;
		}
		else{
			y->count--;
			y->size--;
			if(y->count) return y;
			Node *interN=y->Right,*interfN;
			while(interN->Left!=NULL){
				interfN=interN;
				interN=interN->Left;
			}
			Node* R=interN->Right==NULL?NULL:interN->Right;
			int interi=interN->num;
			delete interN;
			interfN->Left=R;
			y->num=interi;
			return y;
		}
	}
	else if(x<y->num) y->Left=remove(x,y->Left);
	else y->Right=remove(x,y->Right);
	y->size--;	
	return Avalon(y);
}
ll SearchRank(ll x,Node* y){
	if(y->num==x) return (y->Left==NULL?1:y->Left->size+1);
	if(y->Left==NULL&&y->Right==NULL) return 1;
	if(x<y->num) return (y->Left==NULL)?1:SearchRank(x,y->Left);
	return (y->Right==NULL?1:SearchRank(x,y->Right))+(y->Left==NULL?0:y->Left->size)+y->count;
}
ll SearchNumber(ll x,Node* y){
	int leftsize=(y->Left==NULL?0:y->Left->size);
	if(x<=leftsize) return SearchNumber(x,y->Left);
	if(x<=leftsize+y->count) return y->num;
	return SearchNumber(x-leftsize-y->count,y->Right);
}
ll FindPre(ll x,Node* y){
	ll Min=ovrmin;
	Node* interN=y;
	while(interN!=NULL){
		if(x<interN->num) interN=interN->Left;
		else if(x>interN->num){
			Min=max(Min,interN->num);
			interN=interN->Right;
		}
		else{
			interN=interN->Left;
			while(interN!=NULL){
				if(interN->num<x) Min=max(Min,interN->num);
				interN=interN->Right;
			}
		}
	}
	return Min;
}
ll FindSuc(ll x,Node* y){
	ll Max=ovrmax;
	Node* interN=y;
	while(interN!=NULL){
		if(x<interN->num){
			Max=min(Max,interN->num);
			interN=interN->Left;
		}
		else if(x>interN->num) interN=interN->Right;
		else{
			interN=interN->Right;
			while(interN!=NULL){
				if(interN->num>x) Max=min(Max,interN->num);
				interN=interN->Left;
			}
		}
	}
	return Max;
}
void operate(){
	cin>>opt>>num;
	switch(opt){
		case 1:
			Root=add(num,Root);
			break;
		case 2:
			Root=remove(num,Root);
			break;
		case 3:
			cout<<SearchRank(num,Root)<<endl;
			break;
		case 4:
			cout<<SearchNumber(num,Root)<<endl;
			break;
		case 5:
			cout<<FindPre(num,Root)<<endl;
			break;
		case 6:
			cout<</*"6 "<<num<<endl<<"结果"<<*/FindSuc(num,Root)<<endl;
			break;
		default:
			break;		
	}

}
int main(int argc, char** argv) {
	cin>>asks;
	while(asks--) operate();
	return 0;
}

写的AVL树，用的Win10系统。在本地结果是对的，在洛谷上非说有错。

救救萌新吧，第二天碰电脑QAQ