模板—splay

 #include<iostream>
 #include<cstdio>
 #define cin(x) scanf("%d",&x)
 using namespace std;
 int ch[][],key[],
     cnt[],size[],sz,rt,f[];
 bool get(int x)
 {
     return ch[f[x]][]==x;
 }
 void clear(int x)
 {
     f[x]=cnt[x]=ch[x][]=ch[x][]=size[x]=key[x]=;
 }
 void pushup(int x)
 {
     if(x)
     {
         size[x]=cnt[x];
         if(ch[x][])size[x]+=size[ch[x][]];
         if(ch[x][])size[x]+=size[ch[x][]];
     }
 }
 void rotate(int x)
 {
     int old=f[x],oldf=f[old],which=get(x);
     ch[old][which]=ch[x][which^];f[ch[old][which]]=old;
     ch[x][which^]=old;f[old]=x;
     f[x]=oldf;
     if(oldf)ch[oldf][ch[oldf][]==old]=x;
     pushup(old),pushup(x);
 }
 void splay(int x)
 {
     for(int fa;fa=f[x];rotate(x))
         if(f[fa])
             rotate(get(x)==get(fa)?fa:x);
     rt=x;
 }
 void insert(int x)
 {
     if(rt==)
     {
         sz++;key[sz]=x;rt=sz;
         cnt[sz]=size[sz]=;
         f[sz]=ch[sz][]=ch[sz][]=;
         return;
     }
     int now=rt,fa=;
     while()
     {
         if(x==key[now])
         {
             cnt[now]++;
             pushup(now);
             pushup(fa);
             splay(now);
             return;
         }
         fa=now;
         now=ch[now][x>key[now]];
         if(now==)
         {
             sz++;
             size[sz]=cnt[sz]=;
             ch[sz][]=ch[sz][]=;
             ch[fa][x>key[fa]]=sz;
             f[sz]=fa;
             key[sz]=x;
             pushup(fa);
             splay(sz);
             return;
         }
     }
 }
 int rnk(int x)
 {
     int now=rt,ans=;
     while()
     {
         if(ch[now][] && x<key[now])now=ch[now][];
         else
         {
             ans+=size[ch[now][]];
             if(x==key[now])
             {
                 splay(now);
                 return ans+;
             }
             ans+=cnt[now];
             now=ch[now][];
         }
     }
 }
 int kth(int x)
 {
     int now=rt;
     while()
     {
         if(ch[now][] && x<=size[ch[now][]])now=ch[now][];
         else
         {
             int temp=size[ch[now][]]+cnt[now];
             if(temp>=x)
                 return key[now];
             x-=temp;now=ch[now][];
         }
     }
 }
 int pre()
 {
     int now=ch[rt][];
     while(ch[now][])now=ch[now][];
     return now;
 }
 int next()
 {
     int now=ch[rt][];
     while(ch[now][])now=ch[now][];
     return now;
 }
 void del(int x)
 {
     rnk(x);
     if(cnt[rt]>){cnt[rt]--;pushup(rt);return;}
     if(!ch[rt][] && !ch[rt][]){clear(rt);rt=;return;}
     if(!ch[rt][])
     {
         int old=rt;rt=ch[rt][];f[rt]=;clear(old);return;
     }
     else if(!ch[rt][])
     {
         int old=rt;rt=ch[rt][];f[rt]=;clear(old);return;
     }
     int oldrt=rt,leftbig=pre();
     splay(leftbig);//leftbig无儿子，所以oldrt无左二子
     ch[rt][]=ch[oldrt][];
     f[ch[oldrt][]]=rt;
     clear(oldrt);
     pushup(rt);

 }
 signed main()
 {
 //    freopen("input5.in","r",stdin);

     int n,opt,x;
     cin(n);
     while(n--)
     {
         cin(opt);cin(x);
         if(opt==)insert(x);
         if(opt==)del(x);
         if(opt==)printf("%ld\n",rnk(x));
         if(opt==)printf("%ld\n",kth(x));
         if(opt==){insert(x);printf("%ld\n",key[pre()]);del(x);}
         if(opt==){insert(x);printf("%ld\n",key[next()]);del(x);}
     }
 }