ORDERSET  Order statistic set
English  Vietnamese 
In this problem, you have to maintain a dynamic set of numbers which support the two fundamental operations
 INSERT(S,x): if x is not in S, insert x into S
 DELETE(S,x): if x is in S, delete x from S
and the two type of queries
 KTH(S) : return the kth smallest element of S
 COUNT(S,x): return the number of elements of S smaller than x
Input
 Line 1: Q (1 ≤ Q ≤ 200000), the number of operations
 In the next Q lines, the first token of each line is a character I, D, K or C meaning that the corresponding operation is INSERT, DELETE, KTH or COUNT, respectively, following by a whitespace and an integer which is the parameter for that operation.
If the parameter is a value x, it is guaranteed that 0 ≤ x ≤ 10^{9}. If the parameter is an index k, it is guaranteed that 1 ≤ k ≤ 10^{9}.
Output
For each query, print the corresponding result in a single line. In particular, for the queries KTH, if k is larger than the number of elements in S, print the word 'invalid'.
Example
Input 8 I 1 I 1 I 2 C 0 K 2 D 1 K 1 K 2 Output 1 2 2 invalid
hide comments
sarwar__05:
20171210 00:08:14
TLE with std::map, AC with std::unordered_map 

amulyagaur:
20171020 07:06:57
Direct implementation of policy based data structures in C++ 

shubham_7616:
20170817 22:08:43
Just loved it......Learned a lot !!


starbot:
20170817 20:19:00
Amazing problem...learnt a lot...time to play cs 

fz0718:
20170725 04:34:21
The four magic lines of code... :)


akt_1998:
20170703 11:29:26
Must do question for beginners in BIT 

rajeev_mnnit:
20170625 14:23:40
somthing new... Tree policy ;) Last edit: 20170625 14:24:07 

leafbebop:
20170606 14:36:48
Having trouble to compress my code.


atulshanbhag:
20170330 15:11:01
Do not print invalid on delete if number does not exist! cost me 7 WAs :( 

jedyn:
20170325 21:23:49
isn't time limit too strict for java? @Duc 
Added by:  Duc 
Date:  20081028 
Time limit:  0.300s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  © VNOI 