Language: C++

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

int main(){
    int n;
    cin >> n;
    vector<pair<int,int>> red(n*2),blue(n*2);
    for(int i=0;i<n;i++)cin >> red[i][0] >> red[i][1];
    for(int i=0;i<n;i++)cin >> blue[i][0] >> blue[i][1];
    sort(red.begin(),red.end());
    sort(blue.begin(),red.end());

    int ans;
    int red_max_y=0;
    int i,j;
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            if(red[j][0]<blue[i][0]&&red[j][1]<blue[i][1])
            {
                if(red_max_y<red[j][1])ans=j;
                red_max_y=max(red_max_y,red[j][1]);
            }
        }
        blue[ans][1]=-1;
    }

    ans=0;
    for(i=0;i<n;i++)
    {
        if(blue[i]==-1)
        {
        ans++;
        }
    }

    cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:38: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
    8 |     for(int i=0;i<n;i++)cin >> red[i][0] >> red[i][1];
      |                                      ^
a.cc:8:51: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
    8 |     for(int i=0;i<n;i++)cin >> red[i][0] >> red[i][1];
      |                                                   ^
a.cc:9:39: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
    9 |     for(int i=0;i<n;i++)cin >> blue[i][0] >> blue[i][1];
      |                                       ^
a.cc:9:53: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
    9 |     for(int i=0;i<n;i++)cin >> blue[i][0] >> blue[i][1];
      |                                                     ^
a.cc:20:22: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   20 |             if(red[j][0]<blue[i][0]&&red[j][1]<blue[i][1])
      |                      ^
a.cc:20:33: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   20 |             if(red[j][0]<blue[i][0]&&red[j][1]<blue[i][1])
      |                                 ^
a.cc:20:44: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   20 |             if(red[j][0]<blue[i][0]&&red[j][1]<blue[i][1])
      |                                            ^
a.cc:20:55: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   20 |             if(red[j][0]<blue[i][0]&&red[j][1]<blue[i][1])
      |                                                       ^
a.cc:22:36: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   22 |                 if(red_max_y<red[j][1])ans=j;
      |                                    ^
a.cc:23:47: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   23 |                 red_max_y=max(red_max_y,red[j][1]);
      |                                               ^
a.cc:26:18: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   26 |         blue[ans][1]=-1;
      |                  ^
a.cc:32:19: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and 'int')
   32 |         if(blue[i]==-1)
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   32 |         if(blue[i]==-1)
      |                      ^
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   32 |         if(blue[i]==-1)
      |                      ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   mismatched types 'const std::pair<_T1, _T2>' and 'int'
   32 |         if(blue[i]==-1)
      |                      ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:32:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int