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
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 

hasan356:
20170317 21:16:21
Learned a lot !! 

s_jindal00:
20170304 21:19:07
Take care of 'invalid'. Don't print 'INVALID'! costed me 1 WA! 

surayans tiwari(http://bit.ly/1EPzcpv):
20170115 05:12:54
nice !! 

geoffreymace7:
20170101 13:18:13
map container gives TLE, use unordered_map instead. 

rihaz_zahir:
20161229 10:39:23
I have used segment tree+coordinate compression to solve with O(QlogN) complexity.


rohitranjan017:
20160830 22:30:12
map > TLE


rohit96:
20160602 21:59:11
tree policy 

Nguyen Cuong:
20160520 05:06:48
compression + BIT + binary search ~ O(n log^2(n)) got AC ^^ 
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 