Dynamic Rankings

#include<iostream>
#include<algorithm>
#include<cstdio>
#define ll long long
#define N 200005
#define lowbit(x) (x & -x)

ll n,m;

ll a[N],num[N << 1];//数集 

struct P{
  int opt;
  ll l,r,k;
}e[N];

ll head[N];//树状数组对应的线段树的头结点。 

struct E{ll ls,rs,val;}T[N * 400]; 

#define l(x) T[x].ls
#define r(x) T[x].rs
#define v(x) T[x].val 
#define mid ((l + r) >> 1) 

ll cnt;

inline void add(ll &now,int l,int r,int to,int ki){
  if(!now)now = ++cnt;
//	std::cout<<now<<" "<<l<<" "<<r<<" "<<to<<" "<<ki<<std::endl; 	
  v(now) += ki;
  if(l == r)return;
  if(to <= mid)
  add(l(now),l,mid,to,ki);
  else
  add(r(now),mid + 1,r,to,ki);
}

inline void change(int now,int val){
  ll k = std::lower_bound(num + 1,num + num[0] + 1,a[now]) - num;
  for(int i = now;i <= num[0];i += lowbit(i))
  add(head[i],1,num[0],k,val);
}

ll t1[N << 2],t2[N << 2];

inline ll find(int l,int r,int k){
//	std::cout<<l<<" "<<r<<" "<<k<<std::endl;
  if(l == r)return l;
  ll sum = 0;
  for(int i = 1;i <= t2[0];++i)
  sum += v(l(t2[i]));
  for(int i = 1;i <= t1[0];++i)
  sum -= v(l(t1[i]));
//	std::cout<<sum<<std::endl;
  if(sum >= k){
  	for(int i = 1;i <= t1[0];++i)
  	t1[i] = l(t1[i]);
  	for(int i = 1;i <= t2[0];++i)
  	t2[i] = l(t2[i]);
  	return find(l,mid,k);
  }
  else{
  	for(int i = 1;i <= t1[0];++i)
  	t1[i] = r(t1[i]); 
  	for(int i = 1;i <= t2[0];++i)
  	t2[i] = r(t2[i]);
  	return find(mid + 1,r,k - sum);
  }
}

inline ll pre(ll l,ll r,ll k){
  t1[0] = 0;
  t2[0] = 0;
  for(int i = l - 1;i;i -= lowbit(i))
  t1[++t1[0]] = head[i];
  for(int i = r;i;i -= lowbit(i))
  t2[++t2[0]] = head[i];
//	for(int i = 1;i <= t1[0];++i)
//	std::cout<<t1[i]<<" ";
//	puts("");
//	for(int i = 1;i <= t2[0];++i)
//	std::cout<<t2[i]<<" "; 
//	puts("");
  return find(1,num[0],k);
} 

int main(){
  scanf("%lld%lld",&n,&m);
  for(int i = 1;i <= n;++i)
  scanf("%lld",&a[i]),num[++num[0]] = a[i];
  for(int i = 1;i <= m;++i){
  	char a;
  	while(a != 'Q' && a != 'C')
  	a = getchar();
  	if(a == 'Q'){
  		e[i].opt = 1;
  		scanf("%lld%lld%lld",&e[i].l,&e[i].r,&e[i].k);
  	}else{
  		e[i].opt = 2;
  		scanf("%lld%lld",&e[i].k,&e[i].l);
  		num[++num[0]] = e[i].l;
  	}
  	a = 'z';
  }
  std::sort(num + 1,num + num[0] + 1);
  num[0] = std::unique(num + 1,num + num[0] + 1) - num - 1;
  for(int i = 1;i <= n;++i)
  change(i,1);
//	for(int i = 1;i <= n;++i)
//	std::cout<<head[i]<<std::endl;
  for(int i = 1;i <= m;++i){
  	if(e[i].opt == 1){
  		std::cout<<num[pre(e[i].l,e[i].r,e[i].k)]<<std::endl;
  	}else{
  		change(e[i].k,-1);
  		a[e[i].k] = e[i].l;
  		change(e[i].k,1);
  	} 
  }
}