Language: C++

#include <bits/stdc++.h>
using namespace std;

#define int long long int
#define pb push_back
#define pi pair<int, int>
#define fir first
#define sec second
#define MAXN 300005
#define mod 1000000007

vector<pi> adj[MAXN];
vector<pi> adj2[MAXN];
set<int> s;

signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, m, q;
  cin >> n >> m >> q;
  for (int i = 0; i < q; i++)
  {
    int a, b;
    cin >> a >> b;
    a--, b--;
    adj[a].pb({a, b});
    adj2[b].pb({a, b});
  }
  int ans = 0;
  for (int i = 0; i < n; i++)
  {
    for (int j = 0; j < m; j++)
    {
      s.clear();
      for (auto const &k : adj[i])
        s.insert(k);
      for (auto const &k : adj2[j])
        s.insert(k);
      ans = max(ans, (int)s.size());
    }
  }
  cout << ans << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:37:17: error: no matching function for call to 'std::set<long long int>::insert(const std::pair<long long int, long long int>&)'
   37 |         s.insert(k);
      |         ~~~~~~~~^~~
In file included from /usr/include/c++/14/set:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:158,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_set.h:568:9: note: candidate: 'template<class _InputIterator> void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>]'
  568 |         insert(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~
/usr/include/c++/14/bits/stl_set.h:568:9: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_set.h:511:7: note: candidate: 'std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(const value_type&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other = std::allocator<long long int>; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key> = __gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::rebind<long long int>; typename _Alloc::value_type = long long int; value_type = long long int]'
  511 |       insert(const value_type& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:511:32: note:   no known conversion for argument 1 from 'const std::pair<long long int, long long int>' to 'const std::set<long long int>::value_type&' {aka 'const long long int&'}
  511 |       insert(const value_type& __x)
      |              ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_set.h:520:7: note: candidate: 'std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(value_type&&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other = std::allocator<long long int>; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key> = __gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::rebind<long long int>; typename _Alloc::value_type = long long int; value_type = long long int]'
  520 |       insert(value_type&& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:520:27: note:   no known conversion for argument 1 from 'const std::pair<long long int, long long int>' to 'std::set<long long int>::value_type&&' {aka 'long long int&&'}
  520 |       insert(value_type&& __x)
      |              ~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_set.h:548:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::insert(const_iterator, const value_type&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; value_type = long long int]'
  548 |       insert(const_iterator __position, const value_type& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:548:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_set.h:553:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::insert(const_iterator, value_type&&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; value_type = long long int]'
  553 |       insert(const_iterator __position, value_type&& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:553:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_set.h:580:7: note: candidate: 'void std::set<_Key, _Compare, _Alloc>::insert(std::initializer_list<_Tp>) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>]'
  580 |       insert(initializer_list<value_type> __l)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:580:43: note:   no known conversion for argument 1 from 'const std::pair<long long int, long long int>' to 'std::initializer_list<long long int>'
  580 |       insert(initializer_list<value_type> __l)
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_set.h:600:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::insert_return_type std::set<_Key, _Compare, _Alloc>::insert(node_type&&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; insert_return_type = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::insert_return_type; node_type = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::node_type]'
  600 |       insert(node_type&& __nh)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:600:26: note:   no known conversion for argument 1 from 'const std::pair<long long int, long long int>' to 'std::set<long long int>::node_type&&' {aka 'std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::node_type&&'}
  600 |       insert(node_type&& __nh)
      |              ~~~~~~~~~~~~^~~~
/usr/include/c++/14/bits/stl_set.h:605:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::insert(const_iterator, node_type&&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; node_type = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::node_type]'
  605 |       insert(const_iterator __hint, node_type&& __nh)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:605:7: note:   candidate expects 2 arguments, 1 provided
a.cc:39:17: error: no matching function for call to 'std::set<long long int>::insert(const std::pair<long long int, long long int>&)'
   39 |         s.insert(k);
      |         ~~~~~~~~^~~
/usr/include/c++/14/bits/stl_set.h:568:9: note: candidate: 'template<class _InputIterator> void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>]'
  568 |         insert(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~
/usr/include/c++/14/bits/stl_set.h:568:9: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_set.h:511:7: note: candidate: 'std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(const value_type&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<long long int>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator = std::_Rb_tree<long long int, long long int, std::_Identity<long long int>, std::less<long long int>, std::allocator<long long int> >::const_iterator; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other = std::allocator<long long int>; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key> = __gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::rebind<long long int>; typename _Alloc::value_type = long long int; value_type = long long int]'
  511 |       insert(const value_type& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_set.h:511:32: note:   no known conversion for argument 1 from 'const std::pair<long long int, long long int>' to 'const std::set<long long int>::value_type&' {aka 'const long long int&'}
  511 |       insert(const value_type& __x)
      |              ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_set.h:520:7: note: candidate: 'std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(value_type&&) [with _Key = long long int; _Compare = std::less<long long int>; _Alloc = std::allocator<lon