In file included from /usr/include/c++/11/map:60,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:81,
                 from answer.code:1:
/usr/include/c++/11/bits/stl_tree.h: In instantiation of ‘static const _Key& std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_S_key(std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Const_Link_type) [with _Key = int; _Val = int; _KeyOfValue = std::_Identity<int>; _Compare = convex_hull_half<std::greater<vec> >::cmp; _Alloc = std::allocator<int>; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Const_Link_type = const std::_Rb_tree_node<int>*]’:
/usr/include/c++/11/bits/stl_tree.h:1971:37:   required from ‘std::pair<std::_Rb_tree_iterator<_Val>, std::_Rb_tree_iterator<_Val> > std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::equal_range(const _Key&) [with _Key = int; _Val = int; _KeyOfValue = std::_Identity<int>; _Compare = convex_hull_half<std::greater<vec> >::cmp; _Alloc = std::allocator<int>]’
/usr/include/c++/11/bits/stl_tree.h:2508:49:   required from ‘std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::size_type std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::erase(const _Key&) [with _Key = int; _Val = int; _KeyOfValue = std::_Identity<int>; _Compare = convex_hull_half<std::greater<vec> >::cmp; _Alloc = std::allocator<int>; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::size_type = long unsigned int]’
/usr/include/c++/11/bits/stl_set.h:685:26:   required from ‘std::set<_Key, _Compare, _Alloc>::size_type std::set<_Key, _Compare, _Alloc>::erase(const key_type&) [with _Key = int; _Compare = convex_hull_half<std::greater<vec> >::cmp; _Alloc = std::allocator<int>; std::set<_Key, _Compare, _Alloc>::size_type = long unsigned int; std::set<_Key, _Compare, _Alloc>::key_type = int]’
answer.code:46:50:   required from ‘bool convex_hull_half<pr>::insert(vec) [with pr = std::greater<vec>]’
answer.code:83:18:   required from here
/usr/include/c++/11/bits/stl_tree.h:770:15: error: static assertion failed: comparison object must be invocable as const
  770 |               is_invocable_v<const _Compare&, const _Key&, const _Key&>,
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/11/bits/stl_tree.h:770:15: note: ‘std::is_invocable_v<const convex_hull_half<std::greater<vec> >::cmp&, const int&, const int&>’ evaluates to false
answer.code: In function ‘int main()’:
answer.code:62:17: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   62 |     int n; scanf("%d", &n);
      |            ~~~~~^~~~~~~~~~
answer.code:70:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   70 |         scanf("%d %d %d", &a, &b, &x);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~