FHQ求调，WA65，悬棺

#include<bits/stdc++.h>
using namespace std;
mt19937 myrand(time(0));
#define int long long 
int n,op,a,ct,root,sum;
struct node{
	int cnt,val,rnd,siz,ls,rs,fa;
}tr[200005];
int newnode(int x){
	tr[++ct].rnd=myrand(),tr[ct].siz=1,tr[ct].val=x;
	return ct;
}
void fen(int ii,int k,int &l,int &r){
	if(ii==0){
		l=0,r=0;
		return;
	}
	if(tr[ii].val<=k){
		l=ii;
		fen(tr[ii].rs,k,tr[ii].rs,r);
	}else{
		r=ii;
		fen(tr[ii].ls,k,l,tr[ii].ls);
	}
	tr[ii].siz=tr[tr[ii].ls].siz+tr[tr[ii].rs].siz+1;
}
int he(int l,int r){
	if(l==0) return r;
	if(r==0) return l;
	if(tr[l].rnd<tr[r].rnd){
		tr[l].rs=he(tr[l].rs,r);
		tr[l].siz=tr[tr[l].ls].siz+tr[tr[l].rs].siz+1;
		return l;
	}else{
		tr[r].ls=he(l,tr[r].ls);
		tr[r].siz=tr[tr[r].ls].siz+tr[tr[r].rs].siz+1;
		return r;
	}
}
void add(int x){
	int l=0,r=0;
	fen(root,x,l,r);
	root=he(he(l,newnode(x)),r);
}
void del(int x){
	int l=0,r=0,mid=0;
	fen(root,x,l,r);
	fen(l,x-1,l,mid);
	root=he(l,r);
}
int askrnd(int x){
	int l=0,r=0;
	fen(root,x-1,l,r);
	sum=tr[l].siz+1;
	root=he(l,r);
	return sum;
}
int askrnd2(int ii,int x){
	if(x==tr[tr[ii].ls].siz+1) return tr[ii].val;
	if(x<=tr[tr[ii].ls].siz) return askrnd2(tr[ii].ls,x);
	return askrnd2(tr[ii].rs,x-tr[tr[ii].ls].siz-1);
}
int ask3(int ii,int x){
	return askrnd2(ii,askrnd(x)-1);
}
int ask4(int ii,int x){
	return askrnd2(ii,askrnd(x+1));
}
signed main(){
	scanf("%lld",&n);
	for(int i=1;i<=n;i++){
		scanf("%lld%lld",&op,&a);
		sum=0;
		if(op==1) add(a);
		if(op==2) del(a);
		if(op==3) printf("%lld\n",askrnd(a));
		if(op==4) printf("%lld\n",askrnd2(root,a));
		if(op==5) printf("%lld\n",ask3(root,a));
		if(op==6) printf("%lld\n",ask4(root,a));
	}
}