Language: C++

#include<iostream>
#include<map>
#include<queue>
#include<algorithm>
using namespace std;

#define fs first
#define sc second
typedef pair<int,int> P;

int n;
P p[200100];

int main(){
  cin >> n;
  for(int i=0;i<n;i++)cin >> p[i].fs >> p[i].sc;
  p[n] = P(1,100001);
  sort(p,p+n+1);

  priority_queue<int, vector<int>, greater<int> > q;
  int ans = 1;

  for(int i=0;i<=n;i++){
    while(!q.empty() && q.top() < p[i].fs)q.pop();
    q.push(p[i].sc);    
    if(p[i].fs <= q.size() && q.size() <= q.top())ans = max(ans,q.size());
  }

  cout << ans-1 << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:26:60: error: no matching function for call to 'max(int&, std::priority_queue<int, std::vector<int>, std::greater<int> >::size_type)'
   26 |     if(p[i].fs <= q.size() && q.size() <= q.top())ans = max(ans,q.size());
      |                                                         ~~~^~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:26:60: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::priority_queue<int, std::vector<int>, std::greater<int> >::size_type' {aka 'long unsigned int'})
   26 |     if(p[i].fs <= q.size() && q.size() <= q.top())ans = max(ans,q.size());
      |                                                         ~~~^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:26:60: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   26 |     if(p[i].fs <= q.size() && q.size() <= q.top())ans = max(ans,q.size());
      |                                                         ~~~^~~~~~~~~~~~~~