struct Treap {    struct node {        node *son[2];        int key,siz,wei,cnt;        node(int _key,node *f) {            son[0]=son[1]=f;            key=_key;siz=cnt=1;wei=rand();        }        void pushup() {            siz=son[0]->siz+son[1]->siz+cnt;        }    }*null,*root;    Treap() {        null=new node(0,0);        null->siz=null->siz=0;        null->wei=inf;root=null;//  INF视情况而定    }    void rot(node* &rt,bool d) {        node* c=rt->son[!d];rt->son[!d]=c->son[d];        c->son[d]=rt;rt->pushup();c->pushup();rt=c;    }    void insert(const int &key,node* &rt) {        if (rt==null) {            rt=new node(key,null);return ;        }        if (key==rt->key) {            rt->cnt++;rt->siz++;return ;        }        bool d=key>rt->key;        insert(key,rt->son[d]);        if (rt->wei>rt->son[d]->wei) rot(rt,!d);        rt->pushup();    }    void remove(const int &key,node* &rt) {        if (rt==null) return ;        bool d=key>rt->key;        if (key==rt->key) {            if (rt->cnt>1) {                rt->cnt--;rt->siz--;return ;            }            d=rt->son[0]->wei>rt->son[1]->wei;            if (rt->son[d]==null) {                delete rt;rt=null;return ;            }            rot(rt,!d);remove(key,rt->son[!d]);        } else remove(key,rt->son[d]);        rt->pushup();    }    node* select(int k,node* rt) {        int s=rt->son[0]->siz+rt->cnt;        if (k>=rt->son[0]->siz+1&&k<=s) return rt;        if (s>k) return select(k,rt->son[0]);        else return select(k-s,rt->son[1]);    }    int rank(const int &key,node* rt) {        if (rt==null) return 0;        int s=rt->son[0]->siz+rt->cnt;        if (key==rt->key) return rt->son[0]->siz+1;        if (key<rt->key) return rank(key,rt->son[0]);        else return s+rank(key,rt->son[1]);    }    int pre(const int &k) {        node* t=root;int ret=0;        while (t!=null)        if (t->key<k) ret=t->key,t=t->son[1];        else t=t->son[0];        return ret;    }    int sub(const int &k) {        node* t=root;int ret=0;        while (t!=null)        if (t->key>k) ret=t->key,t=t->son[0];        else t=t->son[1];        return ret;    }};