answer.code:7:31: error: wrong number of template arguments (1, should be at least 2)
    7 | using Set = __gnu_pbds::tree<T>;
      |                               ^
In file included from /usr/include/x86_64-linux-gnu/c++/11/bits/extc++.h:72,
                 from answer.code:2:
/usr/include/c++/11/ext/pb_ds/assoc_container.hpp:635:9: note: provided for ‘template<class Key, class Mapped, class Cmp_Fn, class Tag, template<class Node_CItr, class Node_Itr, class Cmp_Fn_, class _Alloc_> class Node_Update, class _Alloc> class __gnu_pbds::tree’
  635 |   class tree : public PB_DS_TREE_BASE
      |         ^~~~
answer.code:7:25: error: ‘<expression error>’ in namespace ‘__gnu_pbds’ does not name a type
    7 | using Set = __gnu_pbds::tree<T>;
      |                         ^~~~~~~
answer.code:14:3: error: ‘Set’ does not name a type
   14 |   Set<pair<int, int>> s1, s2;
      |   ^~~
answer.code: In constructor ‘Ksm::Ksm()’:
answer.code:16:10: error: class ‘Ksm’ does not have any field named ‘s1’
   16 |   Ksm(): s1{}, s2{}, sm{0} {}
      |          ^~
answer.code:16:16: error: class ‘Ksm’ does not have any field named ‘s2’
   16 |   Ksm(): s1{}, s2{}, sm{0} {}
      |                ^~
answer.code: In member function ‘void Ksm::insert(std::pair<int, int>)’:
answer.code:19:5: error: ‘s1’ was not declared in this scope; did you mean ‘sm’?
   19 |     s1.insert(x);
      |     ^~
      |     sm
answer.code: In member function ‘void Ksm::erase(std::pair<int, int>)’:
answer.code:22:19: error: ‘s1’ was not declared in this scope; did you mean ‘sm’?
   22 |     if (auto it = s1.find(x); it != s1.end()) {
      |                   ^~
      |                   sm
answer.code:26:7: error: ‘s2’ was not declared in this scope; did you mean ‘sm’?
   26 |       s2.erase(x);
      |       ^~
      |       sm
answer.code: In member function ‘lld Ksm::query(int)’:
answer.code:30:12: error: ‘s1’ was not declared in this scope; did you mean ‘sm’?
   30 |     while (s1.size() > k) {
      |            ^~
      |            sm
answer.code:31:7: error: ‘s2’ was not declared in this scope; did you mean ‘sm’?
   31 |       s2.insert(*prev(s1.end()));
      |       ^~
      |       sm
answer.code:35:12: error: ‘s1’ was not declared in this scope; did you mean ‘sm’?
   35 |     while (s1.size() < k) {
      |            ^~
      |            sm
answer.code:36:13: error: ‘s2’ was not declared in this scope; did you mean ‘sm’?
   36 |       sm += s2.begin()->first;
      |             ^~
      |             sm